f(x)=4x*x*x+ax*x+bx+5;f'(x)=12x*x+2ax+bf'(1)=-12;f(1)=-12;4+a+b+5=-12;12+2a+b=-12;解得：a=-3，b=-18
f(x)=4x的三次方-3x的二次方-18x+5由题可列4+a+b+5=-12 12+2a+b=-12解得a=-3 b=-18
