Answer:
511
Step-by-step explanation:
a-b = 7 ____eq 1
ab = 8 ____eq 2
a = 7 + b ___eq 3
a = 8/b ___eq 4
using simultaneous equations :
7 + b = 8/b
7b + b^2=8
b^2 + 7b - 8 =0
factorize it
b^2 + 8b - b - 8 = 0
b(b+8) -1(b+8)=0
b = 1 , -8
then a = 8/1 = 8
a =8/-8 = -1
a = 8, -1
so,
a^3 - b^3
= (8)^3-(1)^3
= 511
