Question 149802
# 1


Let's simplify this expression using synthetic division



Start with the given expression {{{(2x^3 + 7x^2 - 5)/(3+x)}}}


First lets find our test zero:


{{{3+x=0}}} Set the denominator {{{3+x}}} equal to zero


{{{x=-3}}} Solve for x.


so our test zero is -3



Now set up the synthetic division table by placing the test zero in the upper left corner and placing the coefficients of the numerator to the right of the test zero.(note: remember if a polynomial goes from {{{7x^2}}} to {{{-5x^0}}} there is a zero coefficient for {{{x^1}}}. This is simply because {{{2x^3 + 7x^2 - 5}}} really looks like {{{2x^3+7x^2+0x^1+-5x^0}}}<TABLE cellpadding=10><TR><TD>-3</TD><TD>|</TD><TD>2</TD><TD>7</TD><TD>0</TD><TD>-5</TD></TR><TR><TD></TD><TD>|</TD><TD></TD><TD></TD><TD></TD><TD></TD><TD></TD></TR><TR><TD></TD><TD></TD><TD></TD><TD></TD><TD></TD><TD></TD></TR></TABLE>

Start by bringing down the leading coefficient (it is the coefficient with the highest exponent which is 2)

<TABLE cellpadding=10><TR><TD>-3</TD><TD>|</TD><TD>2</TD><TD>7</TD><TD>0</TD><TD>-5</TD></TR><TR><TD></TD><TD>|</TD><TD></TD><TD></TD><TD></TD><TD></TD><TD></TD></TR><TR><TD></TD><TD></TD><TD>2</TD><TD></TD><TD></TD><TD></TD></TR></TABLE>

    Multiply -3 by 2 and place the product (which is -6)  right underneath the second  coefficient (which is 7)

    <TABLE cellpadding=10><TR><TD>-3</TD><TD>|</TD><TD>2</TD><TD>7</TD><TD>0</TD><TD>-5</TD></TR><TR><TD></TD><TD>|</TD><TD></TD><TD>-6</TD><TD></TD><TD></TD><TD></TD></TR><TR><TD></TD><TD></TD><TD>2</TD><TD></TD><TD></TD><TD></TD></TR></TABLE>

    Add -6 and 7 to get 1. Place the sum right underneath -6.

    <TABLE cellpadding=10><TR><TD>-3</TD><TD>|</TD><TD>2</TD><TD>7</TD><TD>0</TD><TD>-5</TD></TR><TR><TD></TD><TD>|</TD><TD></TD><TD>-6</TD><TD></TD><TD></TD><TD></TD></TR><TR><TD></TD><TD></TD><TD>2</TD><TD>1</TD><TD></TD><TD></TD></TR></TABLE>

    Multiply -3 by 1 and place the product (which is -3)  right underneath the third  coefficient (which is 0)

    <TABLE cellpadding=10><TR><TD>-3</TD><TD>|</TD><TD>2</TD><TD>7</TD><TD>0</TD><TD>-5</TD></TR><TR><TD></TD><TD>|</TD><TD></TD><TD>-6</TD><TD>-3</TD><TD></TD><TD></TD></TR><TR><TD></TD><TD></TD><TD>2</TD><TD>1</TD><TD></TD><TD></TD></TR></TABLE>

    Add -3 and 0 to get -3. Place the sum right underneath -3.

    <TABLE cellpadding=10><TR><TD>-3</TD><TD>|</TD><TD>2</TD><TD>7</TD><TD>0</TD><TD>-5</TD></TR><TR><TD></TD><TD>|</TD><TD></TD><TD>-6</TD><TD>-3</TD><TD></TD><TD></TD></TR><TR><TD></TD><TD></TD><TD>2</TD><TD>1</TD><TD>-3</TD><TD></TD></TR></TABLE>

    Multiply -3 by -3 and place the product (which is 9)  right underneath the fourth  coefficient (which is -5)

    <TABLE cellpadding=10><TR><TD>-3</TD><TD>|</TD><TD>2</TD><TD>7</TD><TD>0</TD><TD>-5</TD></TR><TR><TD></TD><TD>|</TD><TD></TD><TD>-6</TD><TD>-3</TD><TD>9</TD><TD></TD></TR><TR><TD></TD><TD></TD><TD>2</TD><TD>1</TD><TD>-3</TD><TD></TD></TR></TABLE>

    Add 9 and -5 to get 4. Place the sum right underneath 9.

    <TABLE cellpadding=10><TR><TD>-3</TD><TD>|</TD><TD>2</TD><TD>7</TD><TD>0</TD><TD>-5</TD></TR><TR><TD></TD><TD>|</TD><TD></TD><TD>-6</TD><TD>-3</TD><TD>9</TD><TD></TD></TR><TR><TD></TD><TD></TD><TD>2</TD><TD>1</TD><TD>-3</TD><TD>4</TD></TR></TABLE>


Since the last column adds to 4, we have a remainder of 4. This means {{{3+x}}} is <b>not</b> a factor of  {{{2x^3 + 7x^2 - 5}}}


Now lets look at the bottom row of coefficients:



The first 3 coefficients (2,1,-3) form the quotient


{{{2x^2 + x - 3}}}


and the last coefficient 4, is the remainder, which is placed over {{{3+x}}} like this


{{{4/(3+x)}}}




Putting this altogether, we get:


{{{2x^2 + x - 3+4/(3+x)}}}


So {{{(2x^3 + 7x^2 - 5)/(3+x)=2x^2 + x - 3+4/(3+x)}}}


which looks like this in remainder form:

{{{(2x^3 + 7x^2 - 5)/(3+x)=2x^2 + x - 3}}} remainder 4




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Answer:


So the quotient is {{{2x^2 + x - 3}}} and the remainder is 4


<hr>


# 2



a)



Any rational zero can be found through this equation


*[Tex \LARGE Roots=\frac{p}{q}] where p and q are the factors of the last and first coefficients



So let's list the factors of 8 (the last coefficient):


*[Tex \LARGE p=\pm1, \pm2, \pm4, \pm8]


Now let's list the factors of 4 (the first coefficient):


*[Tex \LARGE q=\pm1, \pm2, \pm4]


Now let's divide each factor of the last coefficient by each factor of the first coefficient



*[Tex \LARGE \frac{1}{1}, \frac{1}{2}, \frac{1}{4}, \frac{2}{1}, \frac{2}{2}, \frac{2}{4}, \frac{4}{1}, \frac{4}{2}, \frac{4}{4}, \frac{8}{1}, \frac{8}{2}, \frac{8}{4}, -\frac{1}{1}, -\frac{1}{2}, -\frac{1}{4}, -\frac{2}{1}, -\frac{2}{2}, -\frac{2}{4}, -\frac{4}{1}, -\frac{4}{2}, -\frac{4}{4}, -\frac{8}{1}, -\frac{8}{2}, -\frac{8}{4}]







Now simplify


These are all the distinct rational zeros of the function that could occur


*[Tex \LARGE  1, \frac{1}{2}, \frac{1}{4}, 2, 4, 8, -1, -\frac{1}{2}, -\frac{1}{4}, -2, -4, -8]





<hr>



b)



Now let's use synthetic division to test each possible zero:





Let's make the synthetic division table for the function {{{4x^4+5x^3+7x^2-34x+8}}} given the possible zero {{{1/2}}}:

<table cellpadding=10><tr><td>1/2</td><td>|</td><td>4</td><td>5</td><td>7</td><td>-34</td><td>8</td></tr><tr><td></td><td>|</td><td> </td><td>2</td><td>7/2</td><td>21/4</td><td>-115/8</td></tr><tr><td></td><td></td><td>4</td><td>7</td><td>21/2</td><td>-115/4</td><td>-51/8</td></tr></tr></table>

Since the remainder {{{-51/8}}} (the right most entry in the last row) is <font size=4><b>not</b></font> equal to zero, this means that {{{1/2}}} is <font size=4><b>not</b></font> a zero of {{{4x^4+5x^3+7x^2-34x+8}}}



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Let's make the synthetic division table for the function {{{4x^4+5x^3+7x^2-34x+8}}} given the possible zero {{{1/4}}}:

<table cellpadding=10><tr><td>1/4</td><td>|</td><td>4</td><td>5</td><td>7</td><td>-34</td><td>8</td></tr><tr><td></td><td>|</td><td> </td><td>1</td><td>3/2</td><td>17/8</td><td>-255/32</td></tr><tr><td></td><td></td><td>4</td><td>6</td><td>17/2</td><td>-255/8</td><td>1/32</td></tr></tr></table>

Since the remainder {{{1/32}}} (the right most entry in the last row) is <font size=4><b>not</b></font> equal to zero, this means that {{{1/4}}} is <font size=4><b>not</b></font> a zero of {{{4x^4+5x^3+7x^2-34x+8}}}



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Let's make the synthetic division table for the function {{{4x^4+5x^3+7x^2-34x+8}}} given the possible zero {{{2}}}:

<table cellpadding=10><tr><td>2</td><td>|</td><td>4</td><td>5</td><td>7</td><td>-34</td><td>8</td></tr><tr><td></td><td>|</td><td> </td><td>8</td><td>26</td><td>66</td><td>64</td></tr><tr><td></td><td></td><td>4</td><td>13</td><td>33</td><td>32</td><td>72</td></tr></tr></table>

Since the remainder {{{72}}} (the right most entry in the last row) is <font size=4><b>not</b></font> equal to zero, this means that {{{2}}} is <font size=4><b>not</b></font> a zero of {{{4x^4+5x^3+7x^2-34x+8}}}



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Let's make the synthetic division table for the function {{{4x^4+5x^3+7x^2-34x+8}}} given the possible zero {{{4}}}:

<table cellpadding=10><tr><td>4</td><td>|</td><td>4</td><td>5</td><td>7</td><td>-34</td><td>8</td></tr><tr><td></td><td>|</td><td> </td><td>16</td><td>84</td><td>364</td><td>1320</td></tr><tr><td></td><td></td><td>4</td><td>21</td><td>91</td><td>330</td><td>1328</td></tr></tr></table>

Since the remainder {{{1328}}} (the right most entry in the last row) is <font size=4><b>not</b></font> equal to zero, this means that {{{4}}} is <font size=4><b>not</b></font> a zero of {{{4x^4+5x^3+7x^2-34x+8}}}



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Let's make the synthetic division table for the function {{{4x^4+5x^3+7x^2-34x+8}}} given the possible zero {{{8}}}:

<table cellpadding=10><tr><td>8</td><td>|</td><td>4</td><td>5</td><td>7</td><td>-34</td><td>8</td></tr><tr><td></td><td>|</td><td> </td><td>32</td><td>296</td><td>2424</td><td>19120</td></tr><tr><td></td><td></td><td>4</td><td>37</td><td>303</td><td>2390</td><td>19128</td></tr></tr></table>

Since the remainder {{{19128}}} (the right most entry in the last row) is <font size=4><b>not</b></font> equal to zero, this means that {{{8}}} is <font size=4><b>not</b></font> a zero of {{{4x^4+5x^3+7x^2-34x+8}}}



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Let's make the synthetic division table for the function {{{4x^4+5x^3+7x^2-34x+8}}} given the possible zero {{{-1}}}:

<table cellpadding=10><tr><td>-1</td><td>|</td><td>4</td><td>5</td><td>7</td><td>-34</td><td>8</td></tr><tr><td></td><td>|</td><td> </td><td>-4</td><td>-1</td><td>-6</td><td>40</td></tr><tr><td></td><td></td><td>4</td><td>1</td><td>6</td><td>-40</td><td>48</td></tr></tr></table>

Since the remainder {{{48}}} (the right most entry in the last row) is <font size=4><b>not</b></font> equal to zero, this means that {{{-1}}} is <font size=4><b>not</b></font> a zero of {{{4x^4+5x^3+7x^2-34x+8}}}



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Let's make the synthetic division table for the function {{{4x^4+5x^3+7x^2-34x+8}}} given the possible zero {{{-1/2}}}:

<table cellpadding=10><tr><td>-1/2</td><td>|</td><td>4</td><td>5</td><td>7</td><td>-34</td><td>8</td></tr><tr><td></td><td>|</td><td> </td><td>-2</td><td>-3/2</td><td>-11/4</td><td>147/8</td></tr><tr><td></td><td></td><td>4</td><td>3</td><td>11/2</td><td>-147/4</td><td>211/8</td></tr></tr></table>

Since the remainder {{{211/8}}} (the right most entry in the last row) is <font size=4><b>not</b></font> equal to zero, this means that {{{-1/2}}} is <font size=4><b>not</b></font> a zero of {{{4x^4+5x^3+7x^2-34x+8}}}



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Let's make the synthetic division table for the function {{{4x^4+5x^3+7x^2-34x+8}}} given the possible zero {{{-1/4}}}:

<table cellpadding=10><tr><td>-1/4</td><td>|</td><td>4</td><td>5</td><td>7</td><td>-34</td><td>8</td></tr><tr><td></td><td>|</td><td> </td><td>-1</td><td>-1</td><td>-3/2</td><td>71/8</td></tr><tr><td></td><td></td><td>4</td><td>4</td><td>6</td><td>-71/2</td><td>135/8</td></tr></tr></table>

Since the remainder {{{135/8}}} (the right most entry in the last row) is <font size=4><b>not</b></font> equal to zero, this means that {{{-1/4}}} is <font size=4><b>not</b></font> a zero of {{{4x^4+5x^3+7x^2-34x+8}}}



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Let's make the synthetic division table for the function {{{4x^4+5x^3+7x^2-34x+8}}} given the possible zero {{{-2}}}:

<table cellpadding=10><tr><td>-2</td><td>|</td><td>4</td><td>5</td><td>7</td><td>-34</td><td>8</td></tr><tr><td></td><td>|</td><td> </td><td>-8</td><td>6</td><td>-26</td><td>120</td></tr><tr><td></td><td></td><td>4</td><td>-3</td><td>13</td><td>-60</td><td>128</td></tr></tr></table>

Since the remainder {{{128}}} (the right most entry in the last row) is <font size=4><b>not</b></font> equal to zero, this means that {{{-2}}} is <font size=4><b>not</b></font> a zero of {{{4x^4+5x^3+7x^2-34x+8}}}



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Let's make the synthetic division table for the function {{{4x^4+5x^3+7x^2-34x+8}}} given the possible zero {{{-4}}}:

<table cellpadding=10><tr><td>-4</td><td>|</td><td>4</td><td>5</td><td>7</td><td>-34</td><td>8</td></tr><tr><td></td><td>|</td><td> </td><td>-16</td><td>44</td><td>-204</td><td>952</td></tr><tr><td></td><td></td><td>4</td><td>-11</td><td>51</td><td>-238</td><td>960</td></tr></tr></table>

Since the remainder {{{960}}} (the right most entry in the last row) is <font size=4><b>not</b></font> equal to zero, this means that {{{-4}}} is <font size=4><b>not</b></font> a zero of {{{4x^4+5x^3+7x^2-34x+8}}}



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Let's make the synthetic division table for the function {{{4x^4+5x^3+7x^2-34x+8}}} given the possible zero {{{-8}}}:

<table cellpadding=10><tr><td>-8</td><td>|</td><td>4</td><td>5</td><td>7</td><td>-34</td><td>8</td></tr><tr><td></td><td>|</td><td> </td><td>-32</td><td>216</td><td>-1784</td><td>14544</td></tr><tr><td></td><td></td><td>4</td><td>-27</td><td>223</td><td>-1818</td><td>14552</td></tr></tr></table>

Since the remainder {{{14552}}} (the right most entry in the last row) is <font size=4><b>not</b></font> equal to zero, this means that {{{-8}}} is <font size=4><b>not</b></font> a zero of {{{4x^4+5x^3+7x^2-34x+8}}}




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Since none of the possible rational roots are actual roots, this means that the polynomial either has irrational roots or complex roots.