f(x)=6x^2+18x+12=0
x=-1,x=-2
单调增则f'(x)>0
6x^2+18x+12>0,x-1
所以单调增区间是(-∞,-2),(-1,+∞)
x1,f(x)增
-2
已知函数f(x)=2x^3-9x^2+12x-3
06x^2+18x+12>0,x-1所以单调增区间是(-∞,-2),(-1,"}}}'>
f(x)=6x^2+18x+12=0
x=-1,x=-2
单调增则f'(x)>0
6x^2+18x+12>0,x-1
所以单调增区间是(-∞,-2),(-1,+∞)
x1,f(x)增
-2