[gon]

ข้อ 6 ตอนที่ 1
ก. จริง) \(y \propto x \Rightarrow y = kx , x^2 + xy + y^2 = x^2 + kx^2 + k^2x^2\)

\(= (1+k+k^2)x^2 = \frac{1+k+k^2}{k}kx^2 = c(kx^2) = c(xy) \Rightarrow x^2 + xy + y^2 \propto xy\)

ข. จริง) \(x^3 + x^2y+y^3 = x^3 + kx^3 + k^3x^3 = (1+k+k^3)x^3 = \frac{1+k+k^3}{k^2}k^2x^3 = c(xy^2) \Rightarrow x^3 + x^2y+y^3 \propto xy^2 \)