SOLUTION: How do you factor bē -20b+51 ?

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Question 117766: How do you factor bē -20b+51 ?
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

Looking at b%5E2-20b%2B51 we can see that the first term is b%5E2 and the last term is 51 where the coefficients are 1 and 51 respectively.

Now multiply the first coefficient 1 and the last coefficient 51 to get 51. Now what two numbers multiply to 51 and add to the middle coefficient -20? Let's list all of the factors of 51:



Factors of 51:
1,3,17,51

-1,-3,-17,-51 ...List the negative factors as well. This will allow us to find all possible combinations

These factors pair up and multiply to 51
1*51
3*17
(-1)*(-51)
(-3)*(-17)

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 NumberSecond NumberSum
1511+51=52
3173+17=20
-1-51-1+(-51)=-52
-3-17-3+(-17)=-20



From this list we can see that -3 and -17 add up to -20 and multiply to 51


Now looking at the expression b%5E2-20b%2B51, replace -20b with -3b%2B-17b (notice -3b%2B-17b adds up to -20b. So it is equivalent to -20b)

b%5E2%2Bhighlight%28-3b%2B-17b%29%2B51


Now let's factor b%5E2-3b-17b%2B51 by grouping:


%28b%5E2-3b%29%2B%28-17b%2B51%29 Group like terms


b%28b-3%29-17%28b-3%29 Factor out the GCF of b out of the first group. Factor out the GCF of -17 out of the second group


%28b-17%29%28b-3%29 Since we have a common term of b-3, we can combine like terms

So b%5E2-3b-17b%2B51 factors to %28b-17%29%28b-3%29


So this also means that b%5E2-20b%2B51 factors to %28b-17%29%28b-3%29 (since b%5E2-20b%2B51 is equivalent to b%5E2-3b-17b%2B51)

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Answer:

So b%5E2-20b%2B51 factors to %28b-17%29%28b-3%29