Question

Factorise y^2-9 show working out​

Answer 1

y² - 9 = (y + 3)(x - 3)

Explanation:

This is a two-term polynomial in which both terms are perfect squares.

It is a difference of two squares.

A difference of two squares factors into the product of a sum and a difference following this pattern:

a² - b² = (a + b)(a - b)

We have

y² - 9 which can be written as y² - 3². Now you see clearly it is the difference of two squares.

y² - 9 = (y + 3)(x - 3)

Answer 2

(y-3)(y+3)

Explanation:

This is a difference of squares.

Difference of squares is when you have a perfect square - another perfect square. You would square root both of them and add one and subtract one.

Solving it without difference of square.

y²+3y-3y-9 is the expanded form and from here you can factor.

You split the equation into two parts.

y²+3y and -3y-9

Factor out any common units.

y(y+3) -3(y+3)

You then put the units outside of parentheses together and the ones inside parentheses together. (The ones inside parentheses should both be the same.

This simplifies to (y-3)(y+3)