Skip to main content
OlympiadHQ

Browse · MATH

Print

jmc

algebra intermediate

Problem

Find the smallest integer value of such that is negative.
Solution
Writing this as an inequality, we get the expression Since -2 and 7 are roots of the quadratic, the inequality must change sign at these two points. Thus, we continue by testing the 3 intervals of . For , both factors of the inequality are negative, thus making it positive. For , only is negative, so the inequality is negative. Finally, for , both factors are positive, making the inequality positive once again. This tells us that the range of that satisfy the inequality is . Since the question asks for the smallest integer value of , the answer is the smallest integer greater than , which is .
Final answer
-1