It is known that the quadratic function f (x) = AX2 + BX + C (a > 0) has two different common points with the X axis If f (c) = 0 and 0 < x < C, f (x) > 0 1) Compare 1 / a with C 2) Proof - 2 < B < 1
Answer: (1) 1 / a > C
According to the known conditions, the symmetry axis - B / (2a) > C has ac0, so B-2;
So - 2 < B < 1 is proved
Then, ac-1 = - (b-2) (formula 3) is changed from (formula 2), because b > - 2, so - (b-2)
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