Question

if 4x-7y=10 and xy= -1 then find the value of 16x^2 +49y^2

Answer 1

4x-7y=10
xy= -1
16x^2+49y^2=?
Solution: -
(a-b) ^2=a^2+b^2-2ab
=>(4x-7y) ^2=(4x) ^2+(7y) ^2-2×4x×7y
=>(10) ^2=16x^2+49y^2-2×28×xy
=>100=16x^2+49y^2-2×28×(-1)
=>100=16x^2+49y^2+56
=>100-56=16x^2+49y^2
=>44=16x^2+49y^2
=>16x^2+49y^2=44

Hence, solved.....