where is the height, in feet, and is the time in seconds.
we want so that is at least 125. remember, i said "at least" means "greater than or equal to" so what we want to find is what 's solve the follwoing inequality:
By the quadratic formula, we have
Now check the intervals on a number line or something. that is, test values that fall in all the regions separated by the x-values. so you would test say,
you can go through the hassle and plug these into the inequality, or just realize it is a downward opening parabola, so the part above zero would be between the two values given. either way, your conclusion should be: