GMAT Practice Question: If y=|3 x-5|-x^2-3, for what value of x will the value of y be greatest?
Question
If y=|3 x-5|-x^2-3, for what value of x will the value of y be greatest?
- -5
- -3/5
- 0
- 3/5
- 5/3
Topics: functions, absolute values, max/min of function
Solution
Step 1
We factor out the negative sign from the denominator to simplify the expression.
y = 3x - 5/-x^2 - 3 = - 3x - 5/x^2 + 3
Step 2
We note that the denominator is always positive, so including the negative sign makes it negative.
x^2 + 3 > 0 -(x^2 + 3) < 0
Step 3
We see that y cannot be positive, so its highest value is zero, which happens when the numerator equals zero.
3x - 5 = 0 3x - 5 = 0 3x = 5 x = 5/3
Answer
5/3
