I am given a probability density function -

f(x) = (1/2)(1-x), for -1 <= x <= 1

For finding the cdf, I distribute the (1/2) and integrate to

F(x) = (1/2)x - (1/4)x^2

My question is how am I able to use this to find the upper and lower quartiles? Every other problem I've done finding the quartiles has just been a linear F(x). Does having a quadratic mean I will have...two upper and low quartiles? That doesn't seem right to me. Any help would be appreciated. Thanks.