Question

If 3a-2b=7,ab=2.Find the value of 27a3-8b3

Answer 1

Answer:

3a-2b=7 ,ab=2..... given

3a-2b=7

squaring both sides

(3a-2b)^2=(7)^2

9a^2-12ab+4b^2 = 49

9a^2-12×2+4b^2 = 49

9a^2-24+4b^2 = 49

9a^2+4b^2 = 49+24

9a^2+4b^2 = 73

a/q.....

27a^3-8b^3

= (3a)^3 - (2b)^3

= (3a-2b) [(3a)^2+6ab+(2b)^2] ........a^3-b^3

= (a-b)(a^2+ab+b^2)

= (7) [9a^2+4b^2+6×2]

= 7 [73+12]

= 7 [ 85]

= 595

hope it helps you