Question 207386

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{{{36t^2+390t+64}}} Start with the given expression.



{{{2(18t^2+195t+32)}}} Factor out the GCF {{{2}}}.



Now let's try to factor the inner expression {{{18t^2+195t+32}}}



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Looking at the expression {{{18t^2+195t+32}}}, we can see that the first coefficient is {{{18}}}, the second coefficient is {{{195}}}, and the last term is {{{32}}}.



Now multiply the first coefficient {{{18}}} by the last term {{{32}}} to get {{{(18)(32)=576}}}.



Now the question is: what two whole numbers multiply to {{{576}}} (the previous product) <font size=4><b>and</b></font> add to the second coefficient {{{195}}}?



To find these two numbers, we need to list <font size=4><b>all</b></font> of the factors of {{{576}}} (the previous product).



Factors of {{{576}}}:

1,2,3,4,6,8,9,12,16,18,24,32,36,48,64,72,96,144,192,288,576

-1,-2,-3,-4,-6,-8,-9,-12,-16,-18,-24,-32,-36,-48,-64,-72,-96,-144,-192,-288,-576



Note: list the negative of each factor. This will allow us to find all possible combinations.



These factors pair up and multiply to {{{576}}}.

1*576 = 576
2*288 = 576
3*192 = 576
4*144 = 576
6*96 = 576
8*72 = 576
9*64 = 576
12*48 = 576
16*36 = 576
18*32 = 576
24*24 = 576
(-1)*(-576) = 576
(-2)*(-288) = 576
(-3)*(-192) = 576
(-4)*(-144) = 576
(-6)*(-96) = 576
(-8)*(-72) = 576
(-9)*(-64) = 576
(-12)*(-48) = 576
(-16)*(-36) = 576
(-18)*(-32) = 576
(-24)*(-24) = 576


Now let's add up each pair of factors to see if one pair adds to the middle coefficient {{{195}}}:



<table border="1"><th>First Number</th><th>Second Number</th><th>Sum</th><tr><td  align="center"><font color=black>1</font></td><td  align="center"><font color=black>576</font></td><td  align="center"><font color=black>1+576=577</font></td></tr><tr><td  align="center"><font color=black>2</font></td><td  align="center"><font color=black>288</font></td><td  align="center"><font color=black>2+288=290</font></td></tr><tr><td  align="center"><font color=red>3</font></td><td  align="center"><font color=red>192</font></td><td  align="center"><font color=red>3+192=195</font></td></tr><tr><td  align="center"><font color=black>4</font></td><td  align="center"><font color=black>144</font></td><td  align="center"><font color=black>4+144=148</font></td></tr><tr><td  align="center"><font color=black>6</font></td><td  align="center"><font color=black>96</font></td><td  align="center"><font color=black>6+96=102</font></td></tr><tr><td  align="center"><font color=black>8</font></td><td  align="center"><font color=black>72</font></td><td  align="center"><font color=black>8+72=80</font></td></tr><tr><td  align="center"><font color=black>9</font></td><td  align="center"><font color=black>64</font></td><td  align="center"><font color=black>9+64=73</font></td></tr><tr><td  align="center"><font color=black>12</font></td><td  align="center"><font color=black>48</font></td><td  align="center"><font color=black>12+48=60</font></td></tr><tr><td  align="center"><font color=black>16</font></td><td  align="center"><font color=black>36</font></td><td  align="center"><font color=black>16+36=52</font></td></tr><tr><td  align="center"><font color=black>18</font></td><td  align="center"><font color=black>32</font></td><td  align="center"><font color=black>18+32=50</font></td></tr><tr><td  align="center"><font color=black>24</font></td><td  align="center"><font color=black>24</font></td><td  align="center"><font color=black>24+24=48</font></td></tr><tr><td  align="center"><font color=black>-1</font></td><td  align="center"><font color=black>-576</font></td><td  align="center"><font color=black>-1+(-576)=-577</font></td></tr><tr><td  align="center"><font color=black>-2</font></td><td  align="center"><font color=black>-288</font></td><td  align="center"><font color=black>-2+(-288)=-290</font></td></tr><tr><td  align="center"><font color=black>-3</font></td><td  align="center"><font color=black>-192</font></td><td  align="center"><font color=black>-3+(-192)=-195</font></td></tr><tr><td  align="center"><font color=black>-4</font></td><td  align="center"><font color=black>-144</font></td><td  align="center"><font color=black>-4+(-144)=-148</font></td></tr><tr><td  align="center"><font color=black>-6</font></td><td  align="center"><font color=black>-96</font></td><td  align="center"><font color=black>-6+(-96)=-102</font></td></tr><tr><td  align="center"><font color=black>-8</font></td><td  align="center"><font color=black>-72</font></td><td  align="center"><font color=black>-8+(-72)=-80</font></td></tr><tr><td  align="center"><font color=black>-9</font></td><td  align="center"><font color=black>-64</font></td><td  align="center"><font color=black>-9+(-64)=-73</font></td></tr><tr><td  align="center"><font color=black>-12</font></td><td  align="center"><font color=black>-48</font></td><td  align="center"><font color=black>-12+(-48)=-60</font></td></tr><tr><td  align="center"><font color=black>-16</font></td><td  align="center"><font color=black>-36</font></td><td  align="center"><font color=black>-16+(-36)=-52</font></td></tr><tr><td  align="center"><font color=black>-18</font></td><td  align="center"><font color=black>-32</font></td><td  align="center"><font color=black>-18+(-32)=-50</font></td></tr><tr><td  align="center"><font color=black>-24</font></td><td  align="center"><font color=black>-24</font></td><td  align="center"><font color=black>-24+(-24)=-48</font></td></tr></table>



From the table, we can see that the two numbers {{{3}}} and {{{192}}} add to {{{195}}} (the middle coefficient).



So the two numbers {{{3}}} and {{{192}}} both multiply to {{{576}}} <font size=4><b>and</b></font> add to {{{195}}}



Now replace the middle term {{{195t}}} with {{{3t+192t}}}. Remember, {{{3}}} and {{{192}}} add to {{{195}}}. So this shows us that {{{3t+192t=195t}}}.



{{{18t^2+highlight(3t+192t)+32}}} Replace the second term {{{195t}}} with {{{3t+192t}}}.



{{{(18t^2+3t)+(192t+32)}}} Group the terms into two pairs.



{{{3t(6t+1)+(192t+32)}}} Factor out the GCF {{{3t}}} from the first group.



{{{3t(6t+1)+32(6t+1)}}} Factor out {{{32}}} from the second group. The goal of this step is to make the terms in the second parenthesis equal to the terms in the first parenthesis.



{{{(3t+32)(6t+1)}}} Combine like terms. Or factor out the common term {{{6t+1}}}



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So {{{2(18t^2+195t+32)}}} then factors further to {{{2(3t+32)(6t+1)}}}



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Answer:



So {{{36t^2+390t+64}}} completely factors to {{{2(3t+32)(6t+1)}}}.



In other words, {{{36t^2+390t+64=2(3t+32)(6t+1)}}}.



Note: you can check the answer by expanding {{{2(3t+32)(6t+1)}}} to get {{{36t^2+390t+64}}} or by graphing the original expression and the answer (the two graphs should be identical).


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