Both 19 and 20 are together. Need help finding right answer

Find the derivative of the function using the formal definition of a derivative. f lim (x + Ax) - f(x) 4X- 0 AX 19) f(*) 8x2 - 4 8 ( X 14X ) - 4 - (8x 1 ) 4X 8 ( x 1 24X + 1 X 2-4- 8x 14 AX AX 2 AX + Ax ? 2 +4 x ) Y 20) x= 1 Using your answer from above, evaluate the derivative at the given x-value. What does this value represent? 2 + AC ) 2 + A X