Question

If 3x+4y=16 and xy=-4,find the value of 9x 2 +16y 2

Answer 1

Answer: 352

Step-by-step explanation:

So what is given is 3x+4y=16

And xy= -4

9x2 + 15y2

(Note - You may get confused with x as multiply sign... don't worry, I will give multiply as "*" :D)

Therefore,

(3x+4y)2 = 9x2 + 16y2 + 2(3x * 4y)

(16)2 = 9x2 + 16y2 + 2(12xy)

= 9x2 + 16y2 + 24*(-4)

= 9x2 + 16y2 - 96

So,

9x2 + 16y2 = 256 + 96

= 352

Hope it helped, friend :)