28. [0.43/1.66 Points] DETAILS PREVIOUS ANSWERS SCALCET9 2.7.032. MY NOTES ASK YOUR T A graphing calculator is recommended. (a) If G(x) = 5x2 - x3, find G'(a) and use it to find equations of the tangent lines to the curve y = 5x2 - x at the points (3, 18) and (4, 16). G'(a) = passing through (3, 18) y, (x) = passing through (4, 16) y, (x) = (b)