Question

If x^2+2y^2 is directly proportion to xy then prove that 2x^2+y^2 is directly proportion to xy

Answer 1

f(x,y)=x^2+2y^2=k xy
where k is proposnality constant
replace x into y
f(x,y) = y^2+2x^2 =k yx
=kxy
means
2x^2+y^2 is directly proportion to xy