证明函数f(x)=根号下x+1再-x,在[-3/4,+∞)内是单调递减

问题描述:

证明函数f(x)=根号下x+1再-x,在[-3/4,+∞)内是单调递减

f(x)=srqt(x+1)-x
f'(x)=1/(2*srqt(x+1))-1
f'(-3/4)=0,且(-3/4,+∞)时,f'(x)