Suppose a parabola y = a x 2 + b x + c has two x intercepts, one positive and one negative, and its vertex…

Suppose a parabola y=ax2+bx+c has two x intercepts, one positive and one negative, and its vertex is (2,-2), then which of the following is true?
  1. ab>0
  2. bc>0
  3. ac>0
  4. a+b+c>0

Solution

Given, y=ax2+bx+c has two x-intercepts one is positive and one is negative and vertex is (2,-2). The graph of y=ax2+bx+c is

Clearly from graph

c>0

-ba>0-b>0

 b<0

f(1)=a+b+c<0

ab<0,ac<0,bc>0

Asked in: BITSAT 2019

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