Question

simplify:(3x+4)³-(3x-4)³​

Answer 1

Answer:

3×5+4=19×19×19=3249

3×5-4=11×11×11=1331

3249-1331=1918

Answer 2

Answer:

a^3-b^3=(a-b)^3+3ab(a-b)

(3x+4)^3-(3x-4)^3

={(3x+4)-(3x-4)}^3+3(3x+4)(3x-4){(3x+4)-(3x-4)}

=(3x+4-3x+4)^3+3{(3x)^2-4^2)}(3x+4-3x+4)

=8+3(9x^2-16).8

=8(1+27x^2-48)

=8(27x^2-47)