Solving quadratic triangle problem.

Question

I keep getting the wrong answer to this : The area is 126cmsquared. The height is 2xcm and the base is x+11cm. Find x.

Answer 1

The area of a triangle is (1/2)(base)(height)

 

So, (1/2)(2x)(x+11) = 126

 

               x(x+11) = 126

 

               x²+11x-126 = 0

 

               (x+18)(x-7) = 0

 

                           x = -18 or 7

 

If x = -18, then the base and height would be negative.  So, x = 7.