Question

If a2 ­ b2 = 8 and a*b = 2, find a4 + b4

Answer 1

Answer:

72

Step-by-step explanation:

Given that:

a^2 - b^2 = 8 ............(1)

ab = 2..................(2)

We need to determine a^4 + b^4

Let us square equation (1).

==> (a^2 - b^2)^2 = 8^2

==> a^4 - 2a^2 b^2 + b^4 = 64

==> a^2 + b^4 = 64 + 2(ab)^2

But from (2) we know that ab= 2

==> a^4 + b^4 = 64 -+2(2^2)

==> a^4 + b^2 = 64 + 8 = 72

==> a^4 + b^4 = 72