Finding a maximum X value for equation.
Im having a hard time finding a maximum value. Well, i can find it, but its not the correct value.
Here is the problem:
A rectangular piece of cardboard measuring 26 inches by 47 inches is to be made into a box with an open top by cutting equal size squares from each corner and folding up the sides. Let X represent the length of each side of each such square. For what value of X will the volume be a maximum ?
So Im thinking the equation is set up like this:
And after foiled out:
and then I apply vertex formula to get the x value: -b/2a= 146/8= 18.25
Wouldnt 18.25 be the x value? Its says the correct answer is 5.37. What am I doing wrong?