Question

Solve the following quadratic equations by factorisation.
x² + x - 90 = 0​

Answer 1

Answer:

Step-by-step explanation:

Factoring x2-x-90

The first term is, x2 its coefficient is 1 .

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

The last term, "the constant", is -90

Step-1 : Multiply the coefficient of the first term by the constant 1 • -90 = -90

Step-2 : Find two factors of -90 whose sum equals the coefficient of the middle term, which is -1 .

-90 + 1 = -89

-45 + 2 = -43

-30 + 3 = -27

-18 + 5 = -13

-15 + 6 = -9

-10 + 9 = -1 That's it

Step-3 : Rewrite the polynomial splitting the middle term using the two factors found in step 2 above, -10 and 9

x2 - 10x + 9x - 90

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

x • (x-10)

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

9 • (x-10)

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

(x+9) • (x-10)

Which is the desired factorization