Question

Напишите ход решения..кто как может

Answer 1

74.
$x_{1}^4*x_{2}^3-x_{1}^3*x_{2}^4=x_{1}^3*x_{2}^3*(x_{1}-x_{2}) = (x_{1}*x_{2})^3*(x_{1}-x_{2}) = \\ =4^3*3=192$

77.
$\frac{37^3+38^3}{25}-3*37*38= \frac{(37+38)*(37^2-37*38+38^2)}{25}-3*37*38= \\ = \frac{75*(37^2-37*38+38^2)}{25} - 3*37*38 = 3*(37^2-37*38+38^2) - \\ -3*37*38 = 3*(37^2-37*38+38^2-37*38) = \\ = 3*(37^2-2*37*38+38^2) = 3*(37-38)^2=3*1=3$