(y + 3)(y - 6)
Explanations:The given quadratic expression is:
[tex]y^2-3y-18[/tex]Multiply the coefficient of y² and the last term
1 x 18 = 18
Look for factors of 18 that can add up to the middle term. That is, -6 and 3
Therefore, instead of writing -3y at the middle as it is in the expression, you write -6y + 3y
The given expression therefore becomes:
[tex]y^2-6y+3y-18[/tex]Factorise the common factors of the first two and the last two terms
[tex]y(y-6)+3(y-6)[/tex]The expression finally becomes:
(y + 3) (y - 6)
