Question 483522


Looking at the expression {{{56b^2+23b-63}}}, we can see that the first coefficient is {{{56}}}, the second coefficient is {{{23}}}, and the last term is {{{-63}}}.



Now multiply the first coefficient {{{56}}} by the last term {{{-63}}} to get {{{(56)(-63)=-3528}}}.



Now the question is: what two whole numbers multiply to {{{-3528}}} (the previous product) <font size=4><b>and</b></font> add to the second coefficient {{{23}}}?



To find these two numbers, we need to list <font size=4><b>all</b></font> of the factors of {{{-3528}}} (the previous product).



Factors of {{{-3528}}}:

1,2,3,4,6,7,8,9,12,14,18,21,24,28,36,42,49,56,63,72,84,98,126,147,168,196,252,294,392,441,504,588,882,1176,1764,3528

-1,-2,-3,-4,-6,-7,-8,-9,-12,-14,-18,-21,-24,-28,-36,-42,-49,-56,-63,-72,-84,-98,-126,-147,-168,-196,-252,-294,-392,-441,-504,-588,-882,-1176,-1764,-3528



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



These factors pair up and multiply to {{{-3528}}}.

1*(-3528) = -3528
2*(-1764) = -3528
3*(-1176) = -3528
4*(-882) = -3528
6*(-588) = -3528
7*(-504) = -3528
8*(-441) = -3528
9*(-392) = -3528
12*(-294) = -3528
14*(-252) = -3528
18*(-196) = -3528
21*(-168) = -3528
24*(-147) = -3528
28*(-126) = -3528
36*(-98) = -3528
42*(-84) = -3528
49*(-72) = -3528
56*(-63) = -3528
(-1)*(3528) = -3528
(-2)*(1764) = -3528
(-3)*(1176) = -3528
(-4)*(882) = -3528
(-6)*(588) = -3528
(-7)*(504) = -3528
(-8)*(441) = -3528
(-9)*(392) = -3528
(-12)*(294) = -3528
(-14)*(252) = -3528
(-18)*(196) = -3528
(-21)*(168) = -3528
(-24)*(147) = -3528
(-28)*(126) = -3528
(-36)*(98) = -3528
(-42)*(84) = -3528
(-49)*(72) = -3528
(-56)*(63) = -3528


Now let's add up each pair of factors to see if one pair adds to the middle coefficient {{{23}}}:



<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>-3528</font></td><td  align="center"><font color=black>1+(-3528)=-3527</font></td></tr><tr><td  align="center"><font color=black>2</font></td><td  align="center"><font color=black>-1764</font></td><td  align="center"><font color=black>2+(-1764)=-1762</font></td></tr><tr><td  align="center"><font color=black>3</font></td><td  align="center"><font color=black>-1176</font></td><td  align="center"><font color=black>3+(-1176)=-1173</font></td></tr><tr><td  align="center"><font color=black>4</font></td><td  align="center"><font color=black>-882</font></td><td  align="center"><font color=black>4+(-882)=-878</font></td></tr><tr><td  align="center"><font color=black>6</font></td><td  align="center"><font color=black>-588</font></td><td  align="center"><font color=black>6+(-588)=-582</font></td></tr><tr><td  align="center"><font color=black>7</font></td><td  align="center"><font color=black>-504</font></td><td  align="center"><font color=black>7+(-504)=-497</font></td></tr><tr><td  align="center"><font color=black>8</font></td><td  align="center"><font color=black>-441</font></td><td  align="center"><font color=black>8+(-441)=-433</font></td></tr><tr><td  align="center"><font color=black>9</font></td><td  align="center"><font color=black>-392</font></td><td  align="center"><font color=black>9+(-392)=-383</font></td></tr><tr><td  align="center"><font color=black>12</font></td><td  align="center"><font color=black>-294</font></td><td  align="center"><font color=black>12+(-294)=-282</font></td></tr><tr><td  align="center"><font color=black>14</font></td><td  align="center"><font color=black>-252</font></td><td  align="center"><font color=black>14+(-252)=-238</font></td></tr><tr><td  align="center"><font color=black>18</font></td><td  align="center"><font color=black>-196</font></td><td  align="center"><font color=black>18+(-196)=-178</font></td></tr><tr><td  align="center"><font color=black>21</font></td><td  align="center"><font color=black>-168</font></td><td  align="center"><font color=black>21+(-168)=-147</font></td></tr><tr><td  align="center"><font color=black>24</font></td><td  align="center"><font color=black>-147</font></td><td  align="center"><font color=black>24+(-147)=-123</font></td></tr><tr><td  align="center"><font color=black>28</font></td><td  align="center"><font color=black>-126</font></td><td  align="center"><font color=black>28+(-126)=-98</font></td></tr><tr><td  align="center"><font color=black>36</font></td><td  align="center"><font color=black>-98</font></td><td  align="center"><font color=black>36+(-98)=-62</font></td></tr><tr><td  align="center"><font color=black>42</font></td><td  align="center"><font color=black>-84</font></td><td  align="center"><font color=black>42+(-84)=-42</font></td></tr><tr><td  align="center"><font color=black>49</font></td><td  align="center"><font color=black>-72</font></td><td  align="center"><font color=black>49+(-72)=-23</font></td></tr><tr><td  align="center"><font color=black>56</font></td><td  align="center"><font color=black>-63</font></td><td  align="center"><font color=black>56+(-63)=-7</font></td></tr><tr><td  align="center"><font color=black>-1</font></td><td  align="center"><font color=black>3528</font></td><td  align="center"><font color=black>-1+3528=3527</font></td></tr><tr><td  align="center"><font color=black>-2</font></td><td  align="center"><font color=black>1764</font></td><td  align="center"><font color=black>-2+1764=1762</font></td></tr><tr><td  align="center"><font color=black>-3</font></td><td  align="center"><font color=black>1176</font></td><td  align="center"><font color=black>-3+1176=1173</font></td></tr><tr><td  align="center"><font color=black>-4</font></td><td  align="center"><font color=black>882</font></td><td  align="center"><font color=black>-4+882=878</font></td></tr><tr><td  align="center"><font color=black>-6</font></td><td  align="center"><font color=black>588</font></td><td  align="center"><font color=black>-6+588=582</font></td></tr><tr><td  align="center"><font color=black>-7</font></td><td  align="center"><font color=black>504</font></td><td  align="center"><font color=black>-7+504=497</font></td></tr><tr><td  align="center"><font color=black>-8</font></td><td  align="center"><font color=black>441</font></td><td  align="center"><font color=black>-8+441=433</font></td></tr><tr><td  align="center"><font color=black>-9</font></td><td  align="center"><font color=black>392</font></td><td  align="center"><font color=black>-9+392=383</font></td></tr><tr><td  align="center"><font color=black>-12</font></td><td  align="center"><font color=black>294</font></td><td  align="center"><font color=black>-12+294=282</font></td></tr><tr><td  align="center"><font color=black>-14</font></td><td  align="center"><font color=black>252</font></td><td  align="center"><font color=black>-14+252=238</font></td></tr><tr><td  align="center"><font color=black>-18</font></td><td  align="center"><font color=black>196</font></td><td  align="center"><font color=black>-18+196=178</font></td></tr><tr><td  align="center"><font color=black>-21</font></td><td  align="center"><font color=black>168</font></td><td  align="center"><font color=black>-21+168=147</font></td></tr><tr><td  align="center"><font color=black>-24</font></td><td  align="center"><font color=black>147</font></td><td  align="center"><font color=black>-24+147=123</font></td></tr><tr><td  align="center"><font color=black>-28</font></td><td  align="center"><font color=black>126</font></td><td  align="center"><font color=black>-28+126=98</font></td></tr><tr><td  align="center"><font color=black>-36</font></td><td  align="center"><font color=black>98</font></td><td  align="center"><font color=black>-36+98=62</font></td></tr><tr><td  align="center"><font color=black>-42</font></td><td  align="center"><font color=black>84</font></td><td  align="center"><font color=black>-42+84=42</font></td></tr><tr><td  align="center"><font color=red>-49</font></td><td  align="center"><font color=red>72</font></td><td  align="center"><font color=red>-49+72=23</font></td></tr><tr><td  align="center"><font color=black>-56</font></td><td  align="center"><font color=black>63</font></td><td  align="center"><font color=black>-56+63=7</font></td></tr></table>



From the table, we can see that the two numbers {{{-49}}} and {{{72}}} add to {{{23}}} (the middle coefficient).



So the two numbers {{{-49}}} and {{{72}}} both multiply to {{{-3528}}} <font size=4><b>and</b></font> add to {{{23}}}



Now replace the middle term {{{23b}}} with {{{-49b+72b}}}. Remember, {{{-49}}} and {{{72}}} add to {{{23}}}. So this shows us that {{{-49b+72b=23b}}}.



{{{56b^2+highlight(-49b+72b)-63}}} Replace the second term {{{23b}}} with {{{-49b+72b}}}.



{{{(56b^2-49b)+(72b-63)}}} Group the terms into two pairs.



{{{7b(8b-7)+(72b-63)}}} Factor out the GCF {{{7b}}} from the first group.



{{{7b(8b-7)+9(8b-7)}}} Factor out {{{9}}} 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.



{{{(7b+9)(8b-7)}}} Combine like terms. Or factor out the common term {{{8b-7}}}



===============================================================



Answer:



So {{{56b^2+23b-63}}} factors to {{{(7b+9)(8b-7)}}}.



In other words, {{{56b^2+23b-63=(7b+9)(8b-7)}}}.



Note: you can check the answer by expanding {{{(7b+9)(8b-7)}}} to get {{{56b^2+23b-63}}} or by graphing the original expression and the answer (the two graphs should be identical).