Question

If a – b = 7, a2+ b2 = 85, find a3 – b3



​

Answer 1

Answer:

721

Step-by-step explanation:

$We\ know\ that\\(a-b)^2=a^2+b^2-2ab\\=>(7)^2=85-2ab\\=>49-85= -2ab\\=>36=2ab\\=>18= ab\\So,\\(a-b)^3=a^3-b^3-3ab(a-b)\\=>(7)^3=a^3-b^3-3*18(7)\\=>343=a^3-b^3-378\\=>343+378 = a^3-b^3\\=>721=z^3-b^3$

721 = a^3-b^3

Pls mark this answer as the Brainliest answer!!!

Answer 2

Answer:

Step-by-step explanation:

a - b = 7

[a - b] square = 7(square)

a(square)+ b(square) -29ab = 49

[ a (square) + b (square)] 29ab = 49

85 - 2ab = 36

ab = 18

Now,

= (a - b(cube)] + 3ab (ab

= [7 (square)]+ 3 x 18 x 7

= 343 + 378

=721