SOLUTION: x^4-20x^3+96x^2 could you help me solve this problem on factoring trinomials.
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Question 171902This question is from textbook
: x^4-20x^3+96x^2 could you help me solve this problem on factoring trinomials.
This question is from textbook
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
Start with the given expression
Factor out the GCF
Now let's focus on the inner expression
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Looking at we can see that the first term is and the last term is where the coefficients are 1 and 96 respectively.
Now multiply the first coefficient 1 and the last coefficient 96 to get 96. Now what two numbers multiply to 96 and add to the middle coefficient -20? Let's list all of the factors of 96:
Factors of 96:
1,2,3,4,6,8,12,16,24,32,48,96
-1,-2,-3,-4,-6,-8,-12,-16,-24,-32,-48,-96 ...List the negative factors as well. This will allow us to find all possible combinations
These factors pair up and multiply to 96
1*96
2*48
3*32
4*24
6*16
8*12
(-1)*(-96)
(-2)*(-48)
(-3)*(-32)
(-4)*(-24)
(-6)*(-16)
(-8)*(-12)
note: remember two negative numbers multiplied together make a positive number
Now which of these pairs add to -20? Lets make a table of all of the pairs of factors we multiplied and see which two numbers add to -20
First Number | Second Number | Sum | 1 | 96 | 1+96=97 |
2 | 48 | 2+48=50 |
3 | 32 | 3+32=35 |
4 | 24 | 4+24=28 |
6 | 16 | 6+16=22 |
8 | 12 | 8+12=20 |
-1 | -96 | -1+(-96)=-97 |
-2 | -48 | -2+(-48)=-50 |
-3 | -32 | -3+(-32)=-35 |
-4 | -24 | -4+(-24)=-28 |
-6 | -16 | -6+(-16)=-22 |
-8 | -12 | -8+(-12)=-20 |
From this list we can see that -8 and -12 add up to -20 and multiply to 96
Now looking at the expression , replace with (notice adds up to . So it is equivalent to )
Now let's factor by grouping:
Group like terms
Factor out the GCF of out of the first group. Factor out the GCF of out of the second group
Since we have a common term of , we can combine like terms
So factors to
So this also means that factors to (since is equivalent to )
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So our expression goes from and factors further to
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Answer:
So factors to
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