Question

Factorise 3x2 – 2xy – y2.

Answer 1

(3x-1y)(x+y)

rewrite(3x-y)(x+y)

Answer 2

ANSWER:

GIVEN:

• P(x)= 3x²-2xy-y²

TO FIND:

• Factorise the above expression.

SOLUTION:

= 3x²-2xy-y²

= 3x²-3xy+xy-y²

= (3x²-3xy)+(xy-y²)

= 3x(x-y)+y(x-y)

= (x-y)(3x+y)

NOTE:

Some important formulas:

(a+b)² = a²+b²+2ab

(a-b)² = a²+b²-2ab

(a+b)(a-b) = a²-b²

(a+b)³ = a³+b³+3ab(a+b)

(a-b)³ = a³-b³-3ab(a-b)

a³+b³ = (a+b)(a²+b²-ab)

a³-b³ = (a-b)(a²+b²+ab)

(a+b)² = (a-b)²+4ab

(a-b)² = (a+b)²-4ab