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28 votes
Which expression is equivalent to 6x² - 7x-20 ?

User Mrhaki
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1 Answer

21 votes
21 votes

Answer:

(3x+4)(2x−5)

Explanation:

The first term is, 6x2 its coefficient is 6 .

The middle term is, -7x its coefficient is -7 .

The last term, "the constant", is -20

Step-1 : Multiply the coefficient of the first term by the constant 6 • -20 = -120

Step-2 : Find two factors of -120 whose sum equals the coefficient of the middle term, which is -7 .

-120 + 1 = -119

-60 + 2 = -58

-40 + 3 = -37

-30 + 4 = -26

-24 + 5 = -19

-20 + 6 = -14

-15 + 8 = -7 That's it

Step-3 : Rewrite the polynomial splitting the middle term using the two factors found in step 2 above, -15 and 8

6x2 - 15x + 8x - 20

Step-4 : Add up the first 2 terms, pulling out like factors :

3x • (2x-5)

Add up the last 2 terms, pulling out common factors :

4 • (2x-5)

Step-5 : Add up the four terms of step 4 :

(3x+4) • (2x-5)

Which is the desired factorization

User Tulani
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2.5k points