If m ≤ f(x) ≤ M for a ≤ x ≤ b, where m is the absolute minimum and M is the absolute maximum of f on the interval [a, b], then
m(b − a) ≤ f(x) dx ≤ M(b − a).
Use this property to estimate the value of the integral.
Correct: Your answer is correct.
Incorrect: Your answer is incorrect.
just do a direct substitution
0 <= 4√x <= 4√9
0 <= 4√x <= 12 on [0,9]