((2+5x)^10)'=[10(2+5x)^(10-1)]×(2+5x)'=10(2+5x)^9×5=50(2+5x)^9
∴y'=[((2+5x)^10)'×x-(2+5x)^10×(x)']/x^2
=[50x(2+5x)^9-(2+5x)^10]/x^2