My friend said that (-x)(-x) equals -x^2. Two negative can not equal a negative. A negative times a negative is a positive so the sign should be changed to a positive in order for it to be correct.
After using the formula to find the height my answer was five. I plugged 5 back into the formala and found that 10 and 14 should be the dimensions. Base 1 is 10 and Base 2 is 14 and when i multiplied the two bases by the height, 5, and 1/2 i ended up with 60. So she will be able to create a 60ft^2 garden.