Question 714299


Looking at the expression {{{16z^2-54z+35}}}, we can see that the first coefficient is {{{16}}}, the second coefficient is {{{-54}}}, and the last term is {{{35}}}.



Now multiply the first coefficient {{{16}}} by the last term {{{35}}} to get {{{(16)(35)=560}}}.



Now the question is: what two whole numbers multiply to {{{560}}} (the previous product) <font size=4><b>and</b></font> add to the second coefficient {{{-54}}}?



To find these two numbers, we need to list <font size=4><b>all</b></font> of the factors of {{{560}}} (the previous product).



Factors of {{{560}}}:

1,2,4,5,7,8,10,14,16,20,28,35,40,56,70,80,112,140,280,560

-1,-2,-4,-5,-7,-8,-10,-14,-16,-20,-28,-35,-40,-56,-70,-80,-112,-140,-280,-560



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



These factors pair up and multiply to {{{560}}}.

1*560 = 560
2*280 = 560
4*140 = 560
5*112 = 560
7*80 = 560
8*70 = 560
10*56 = 560
14*40 = 560
16*35 = 560
20*28 = 560
(-1)*(-560) = 560
(-2)*(-280) = 560
(-4)*(-140) = 560
(-5)*(-112) = 560
(-7)*(-80) = 560
(-8)*(-70) = 560
(-10)*(-56) = 560
(-14)*(-40) = 560
(-16)*(-35) = 560
(-20)*(-28) = 560


Now let's add up each pair of factors to see if one pair adds to the middle coefficient {{{-54}}}:



<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>560</font></td><td  align="center"><font color=black>1+560=561</font></td></tr><tr><td  align="center"><font color=black>2</font></td><td  align="center"><font color=black>280</font></td><td  align="center"><font color=black>2+280=282</font></td></tr><tr><td  align="center"><font color=black>4</font></td><td  align="center"><font color=black>140</font></td><td  align="center"><font color=black>4+140=144</font></td></tr><tr><td  align="center"><font color=black>5</font></td><td  align="center"><font color=black>112</font></td><td  align="center"><font color=black>5+112=117</font></td></tr><tr><td  align="center"><font color=black>7</font></td><td  align="center"><font color=black>80</font></td><td  align="center"><font color=black>7+80=87</font></td></tr><tr><td  align="center"><font color=black>8</font></td><td  align="center"><font color=black>70</font></td><td  align="center"><font color=black>8+70=78</font></td></tr><tr><td  align="center"><font color=black>10</font></td><td  align="center"><font color=black>56</font></td><td  align="center"><font color=black>10+56=66</font></td></tr><tr><td  align="center"><font color=black>14</font></td><td  align="center"><font color=black>40</font></td><td  align="center"><font color=black>14+40=54</font></td></tr><tr><td  align="center"><font color=black>16</font></td><td  align="center"><font color=black>35</font></td><td  align="center"><font color=black>16+35=51</font></td></tr><tr><td  align="center"><font color=black>20</font></td><td  align="center"><font color=black>28</font></td><td  align="center"><font color=black>20+28=48</font></td></tr><tr><td  align="center"><font color=black>-1</font></td><td  align="center"><font color=black>-560</font></td><td  align="center"><font color=black>-1+(-560)=-561</font></td></tr><tr><td  align="center"><font color=black>-2</font></td><td  align="center"><font color=black>-280</font></td><td  align="center"><font color=black>-2+(-280)=-282</font></td></tr><tr><td  align="center"><font color=black>-4</font></td><td  align="center"><font color=black>-140</font></td><td  align="center"><font color=black>-4+(-140)=-144</font></td></tr><tr><td  align="center"><font color=black>-5</font></td><td  align="center"><font color=black>-112</font></td><td  align="center"><font color=black>-5+(-112)=-117</font></td></tr><tr><td  align="center"><font color=black>-7</font></td><td  align="center"><font color=black>-80</font></td><td  align="center"><font color=black>-7+(-80)=-87</font></td></tr><tr><td  align="center"><font color=black>-8</font></td><td  align="center"><font color=black>-70</font></td><td  align="center"><font color=black>-8+(-70)=-78</font></td></tr><tr><td  align="center"><font color=black>-10</font></td><td  align="center"><font color=black>-56</font></td><td  align="center"><font color=black>-10+(-56)=-66</font></td></tr><tr><td  align="center"><font color=red>-14</font></td><td  align="center"><font color=red>-40</font></td><td  align="center"><font color=red>-14+(-40)=-54</font></td></tr><tr><td  align="center"><font color=black>-16</font></td><td  align="center"><font color=black>-35</font></td><td  align="center"><font color=black>-16+(-35)=-51</font></td></tr><tr><td  align="center"><font color=black>-20</font></td><td  align="center"><font color=black>-28</font></td><td  align="center"><font color=black>-20+(-28)=-48</font></td></tr></table>



From the table, we can see that the two numbers {{{-14}}} and {{{-40}}} add to {{{-54}}} (the middle coefficient).



So the two numbers {{{-14}}} and {{{-40}}} both multiply to {{{560}}} <font size=4><b>and</b></font> add to {{{-54}}}



Now replace the middle term {{{-54z}}} with {{{-14z-40z}}}. Remember, {{{-14}}} and {{{-40}}} add to {{{-54}}}. So this shows us that {{{-14z-40z=-54z}}}.



{{{16z^2+highlight(-14z-40z)+35}}} Replace the second term {{{-54z}}} with {{{-14z-40z}}}.



{{{(16z^2-14z)+(-40z+35)}}} Group the terms into two pairs.



{{{2z(8z-7)+(-40z+35)}}} Factor out the GCF {{{2z}}} from the first group.



{{{2z(8z-7)-5(8z-7)}}} Factor out {{{5}}} 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.



{{{(2z-5)(8z-7)}}} Combine like terms. Or factor out the common term {{{8z-7}}}



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Answer:



So {{{16z^2-54z+35}}} factors to {{{(2z-5)(8z-7)}}}.



In other words, {{{16z^2-54z+35=(2z-5)(8z-7)}}}.



Note: you can check the answer by expanding {{{(2z-5)(8z-7)}}} to get {{{16z^2-54z+35}}} or by graphing the original expression and the answer (the two graphs should be identical).