[(nx)²+2(ny)²]/[5(nx)－(ny)]
=[n²x²+2n²y²]/[n(5x－y)]
=n²[x²+2y²]/[n(5x－y)]
=n[x²+2y²]/(5x－y)
把分式(x²+2y²)/(5x－y)中的字母x,y都扩大n倍,那么分式的值会扩大n倍.