Question

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

Answer 1

a² + b² = 9

Add 2ab on both sides,


a² + b² + 2ab = 9 + 2( 4 )


( a + b )² = 9 + 8


( a + b )² = 17 ----: ( 1 )






a² + b² = 9


Add - 2ab on both sides,


a² + b² - 2ab = 9 - 2( 4 )


( a - b )² = 9 - 8

( a - b )² = 1 ------: ( 2 )






Now,

3( a + b )² - ( a - b )²






Putting value(s) from ( 1 ) and ( 2 )


=> 3( 17 )² - 1²

=> 3( 289 ) - 1

=> 867 - 1

=> 866
$.$

Answer 2

Answer:

a ²+ b² =9

ab= 4

(a+b)²=a²+b²+2.a.b

=> 9+2×4

=>17

(a-b)² = a²+b²-2.a.b

=> 9-2×4

=> 1

3(a+b)² - 2(a-b)²

=>3×17 - 2×1

=>51 - 2

=> 49

Hope this is helpful to U ✨