f(X)=3ax2+2bx+c,a+b+c=0,f(0)*f(1)〉0,求证-1〉b/a〉-2解下
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f(X)=3ax2+2bx+c,a+b+c=0,f(0)*f(1)〉0,求证-1〉b/a〉-2解下
f(X)=3ax2+2bx+c,a+b+c=0,f(0)*f(1)〉0,求证-1〉b/a〉-2解下
f(X)=3ax2+2bx+c,a+b+c=0,f(0)*f(1)〉0,求证-1〉b/a〉-2解下
f(X)=3ax2+2bx+c
f(0)=c
f(1)=3a+2b+c
f(0)*f(1)〉0
c(3a+2b+c)>0
因为a+b+c=0
所以c=-a-b
代入不等式
(-a-b)(3a+2b-a-b)>0
(a+b)(2a+b)