When Dy=2xdx and x=2 ∴,? When x=0.02, dy = 4×0.02 = 0.08；; (None of the four options are correct);

18。 Rolle's three conditions are: the function f(x satisfies ①. Continuous in [a, b]; (2) It is derivable at (a, b); ③. f(a)= f(b)。

Observing the four options, only B meets; A. f(x)= 1+∣x∣, when x≤0, f (x) =1-x; F (x) =1+x when x≥0; therefore

The left derivative of f(x) at x=0 =- 1, and the right derivative = 1, that is, f(x) is not derivable at x=0; C. f(x)= 1/(x- 1)，f(-2)=- 1/3

f(2)= 1/3； d .f(x)=x？ + 1，f(-2)=-7； f(2)= 9； (Of course, there are other unsatisfied conditions).

19. Lagrange's second condition: ①. F(x) is continuous in [a, b]; ②F(x) is derivable in (a, b); Observe the four options, a, b and c.

All three are satisfied; Only d is not satisfied. The title should be changed to: (d) Lagrange condition is not met.

Where is this coupon? Three questions have two wrong questions!