高等数学问题

【1】z=(√x+3√y)²∂z/∂x=2(√x+3√y)*(1/2)/√x=1+3√(y/x)∂z/∂y=2(√x+3√y)*(3/2)/√y=3√(x/y)+9【2】z=√(2x+y)∂z/∂x=[(1/2)/√(2x+y)]*2=1/√(2x+y)∂z/∂y=(1/2)/√(2x+y)

1、∂f/∂x1 = 2(√x1 + 3√x2 ) * (√x1)' =2(√x1 + 3√x2 ) * 1/(2√x1) = 1 + 3√x2/√x1；∂f/∂x2 = 2(√x1 + 3√x2 ) * (3√x2)' =2(√x1 + 3√x2 ) * 3/(2√x2) = 3√x1/√x2 + 9；2、∂f/∂x1 = (1/2)(2x1 + x2 ) * (2x1)' =(1/2)(2x1 + x2 ) * 2 =2x1 + x2∂f/∂x2 = (1/2)(2x1 + x2 ) * (x2)' =(1/2)(2x1 + x2 )；