Question

Factorise y² + y - 20 ​

Answer 1

(y + 5)(y - 4)

Explanation:

In order to factorize the quadratic expression y² + y - 20, we can look for two numbers that multiply to the constant term (-20) and add up to the coefficient of the linear term (1). These two numbers are 5 and -4 because:

5 × (-4) = -20

5 + (-4) = 1

Now, we can use these numbers to factorize the expression:

y² + y - 20

= y² + (5-4)x - 20

Distribute bracket:

= y² + 5x - 4x - 20

Take common from each two terms:

= y( y + 5) - 4( y + 5)

Take common again and keep remaining in the bracket.

= (y + 5)(y - 4)

So, the factorization of y² + y - 20 is (y + 5)(y - 4).