Skip to main content
OlympiadHQ

Browse · MATH

Print

jmc

algebra intermediate

Problem

Find all such that . Express your answer in interval notation.
Solution
Subtracting 6 from both sides of the equation, we get the quadratic Since -6 and 1 are both roots of the quadratic, the inequality changes signs at these two points. So, we need to test the signs of three ranges of numbers: , , . When , both and will be negative, thus making the inequality positive. When , only will be negative, thus making the inequality negative. Finally when , both and will be positive, thus making the inequality positive once again. Therefore, the only range of that satisfies the inequality is .
Final answer
(-6, 1)