Question

If 4x²+25y²=41 and xy=2. Find the value of 2x-5y

Answer 1

Given 4x^2 + 25y^2 = 41

= > (2x)^2 + (5y)^2 + 2(2x)(5y) - 2(2x)(5y) = 41

= > (2x - 5y)^2 + 20xy = 41

= > (2x - 5y)^2 + 20(2) = 41

= > (2x - 5y)^2 = 41 - 40

= > (2x - 5y)^2 = 1

= > (2x - 5y) = +1, -1.


Hope this helps!