Question

If 2x + 3y = 5 and xy = 1 then find the value of 4x2 + 9 y.​

Answer 1

Given2x+3y=8 and xy=2,

formula,(a+b) 2 =a 2 +b 2 +2ab

∴(2x+3y) 2 =4x 2 +9y 2 +2(2x)(3y)(2x+3y) 2 =4x 2 +9y 2 +12xy8 2 =4x 2 +9y 2 +12(2)

∴4x 2 +9y 2 =64−24=40