Question

simplify (2x-5y)^3-(2x+5y)^3

Answer 1

(2x-5y)^3-(2x+5y)^3
We can solve this by using (a^3 - b^3)

(2x-5y)^3-(2x+5y)^3
=(2x-5y - 2x -5y) ((2x-5y)^2 + (2x-5y)(2x+5y) + (2x+5y)^2)
= -10y(4x^2+25y^2-20xy + 4x^2 - 25y^2 + 4x^2+25y^2+20xy)
= -10y(12x^2 + 25y^2)
= -120x^2y - 250y^3

Answer 2

hi mate,

(2x-5y)³-(2x+5y)³

a³-b³ = (a-b)(a²+b²+ab)

=> (2x-5y-2x-5y)[{2x-5y}²+{2x+5y}²+(2x-5y)(2x+5y)]

=> -10y(4x²+25y²-20xy+ 4x²+25y²+20xy+4x²-25y²)

(a+b)(a-b) = a²-b²

= -10y(12x²+25y²)

i hope it helps you.