# Calculus-Solved-Why is this wrong?

posted by
**Alaina** on
.

use differentials to approximate the change in f(x) if x changes from 3 to 3.01 and f(x) = (3x^2-26)^10

derivative: 10(3x^2-26)^9

f(x+ delta x)= 1 + 10(3x^2-26)^9 * 0.01

= 1 + 10(0.01) <-- Substitute 3 for x

= 1 + 0.1

= 1.1

delta y= 1.1 - 1

delta y= 0.1

but 0.1 is incorrect. why so?