F(x) decreases; F(x) is concave (convex downward)

Draw a schematic diagram

Integral of S 1=f(x)

S2=f(x) Use the right triangle rule to estimate the integral? Obviously, f(b) on the right is relatively small, so S2 < S 1.

S3=f(x) Calculate the integral by trapezoidal rule? Obviously S3>；; S 1 (let the abscissa be a; B two points are connected; Above the curve)

Option d

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