Question

A + b is equals to 10, a square + b square is equal to 58 then find 8a cube - 27 b cube

Answer 1

a+b =10

(a+b)*2=a*2+b*2+2ab

100=58+2ab

2ab=42

ab=21

now (a-b)*2=(a+b)*2-4ab

(a-b)*2=100-4(21)

(a-b)*2=100-84=16

a-b=√16

a-b=4

a+b=10

now by solving it by adding it both a+b+a-b=10+4

2a=14

a=7

b=3

8(a*3)-27(b*3)

8(343)-27(27)=2744-729=2015