ab为实数,满足a^3-3a^2+5a=1 b^3-3b^2+5b=5,求a+b
问题描述:
ab为实数,满足a^3-3a^2+5a=1 b^3-3b^2+5b=5,求a+b
答
设f(x)=x^3-3x^2+5x
f'(x)=3x^2-6x+5
△=36-4*3*5