（5×10^(-2))^3/(-1/4×10^(-3))²(2.5×10^6)
=(5^3×10^(-6))/(-1/4²×10^(-6))(5/2×10^6)
=(5^3×10^(-6))/(-1/16×10^(-6+6))(5/2)
=(5^3×10^(-6))/(-5/8)
=-8(5^2×10^(-6))
=-200×10^(-6)
=-2×10^2×10^(-6)
=-2×10^(-6+2)
=-2×10^(-4)
x²-x=x(x-1)
y(x-y)²+(y-x)³
=y(x-y)²-(x-y)³
=(x-y)²(y-(x-y))
=(x-y)²(2y-x)
2x²+x+x³
=x(2x+1+x²)
=x(x+1)²