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Rewrite the function by completing the square.
f(x) = x2 + x - 30

1 Answer

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Answer:

1.1 Factoring x2+x-30

The first term is, x2 its coefficient is 1 .

The middle term is, +x its coefficient is 1 .

The last term, "the constant", is -30

Step-1 : Multiply the coefficient of the first term by the constant 1 • -30 = -30

Step-2 : Find two factors of -30 whose sum equals the coefficient of the middle term, which is 1 .

-30 + 1 = -29 -15 + 2 = -13 -10 + 3 = -7 -6 + 5 = -1 -5 + 6 = 1 That's it

Step-3 : Rewrite the polynomial splitting the middle term using the two factors found in step 2 above, -5 and 6

x2 - 5x + 6x - 30

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

x • (x-5)

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

6 • (x-5)

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

(x+6) • (x-5)

Which is the desired factorization

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