Question

Factorize y² - 4y-21​

Answer 1

Answer:

=y^2-7y+3y-21

=y(y-7)+3(y-7)

=(y+3)(y-7)

Answer 2

Step by Step Solution

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STEP

1

:

Trying to factor by splitting the middle term

1.1 Factoring y2-4y-21

The first term is, y2 its coefficient is 1 .

The middle term is, -4y its coefficient is -4 .

The last term, "the constant", is -21

Step-1 : Multiply the coefficient of the first term by the constant 1 • -21 = -21

Step-2 : Find two factors of -21 whose sum equals the coefficient of the middle term, which is -4 .

-21 + 1 = -20

-7 + 3 = -4 That's it

Step-3 : Rewrite the polynomial splitting the middle term using the two factors found in step 2 above, -7 and 3

y2 - 7y + 3y - 21

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

y • (y-7)

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

3 • (y-7)

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

(y+3) • (y-7)

Which is the desired factorization

Final result :

(y + 3) • (y - 7)