Question

Value of 9x + 16y , if 3x–4y=10 and xy= –1 is

Answer 1

Answer:

given 3x–4y=10

          xy = -1

3x–4y=10

on squaring

(3x-4y)²=10²

9x²-24xy+16y=100

given xy=-1

9x²-(24)(-1)+16y²=100

9x²+24+16y²   = 100

9x² +  16y²      =100-24

9x²  +  16 y²    = 76

hence answer is 76.