First slide
Theory of expressions
Question

If the equation ax2 + bx + c = 0 (a > 0) has two real roots α and β such that α<2 and β>2, then which of the following statements is/are true?

Moderate
Solution

    f(x)=ax2+bx+c    f(0)=c<0,D>0     b24ac>0    f(1)<0 and f(1)<0     a|b|+c<0    f(2)<0 and f(2)<0     4a2|b|+c<0

Nothing can be said about f(3) or f(-3), whether it is positive or negative.

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