a = 2.125 (slider from 1 to 4, step 0.0001)
f(x) = If[-6 ≤ x ≤ 2, a^(x)]
f'(x) = If[-6 ≤ x ≤ 2, f'(x)]
M: (1, f(1))
M': (1, f'(1))