The area of a triangle is given by A= base x height. Its base is X feet so A=X x height. We need to find the height. The height is 6 times the base (X) + 1 because it's one more than that. So now the equation is A= X(6X+1). We can distribute the X to get A= 6[tex] X^{2} [/tex] +X.
Hope this helped!