Question

if (3a-2b)=9 and ab=7,find the value of 9a²+4b².

Answer 1

hey !!!

(3a-2b) = 9 --------1)

and ab = 7 ------2)

so, 9a² + 4b² =?

now as we know that

(a-b)² = a² + b² - 2ab

➡by using this identity .

(3a-2b)²= (3a)²+(2b)²-2ab

(3a-2b)²+ 2×3a×2b = 9a² + 4b²

=] 81 + 12ab = 9a²+ 4b²

=> 81 + 12×7

165 Answer ..

hope it helps !!!

#Rajukumar111

Answer 2

Solution:

Given: (3a-2b)=9, and ab=7,

To find: 9a²+4b²


 3a-2b=9
squaring on both the sides,
 we get,

(3a-2b)²=(9)²

(3a)²-2(3a)(2b)+(2b)²=9x9

9a²-12ab+4b²=81

9a²-12(7)+4b²=81

9a²-84+4b²=81

9a²+4b²=81+84

9a²+4b²=165...

hope it helps