Question

find the value of a^3+8b^3,if 12ab=72 and a+2b=8​

Answer 1

Answer:

Let us directly substitute a=2b+6 in the expression a3−8b3−36ab−216 as shown below:

(2b+6)3−8b3−36b(2b+6)−216

=[(2b)3+63+(3×(2b)2×6)+(3×2b×62)]−8b3−72b2−216b−216

(∵(x+y)3=x3+y3+3x2y+3xy2)

=8b3+216+72b2+216b−8b3−72b2−216b−216

=(8b3−8b3)+(72b2−72b2)+(216b−216b)+(216−216)

=