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Any function f(x) is an increasing function in [a,b] if :

(A) x1,x2∈[a,b],f(x1)≥f(x2)x_1, x_2 \in [a, b], f(x_1) \geq f(x_2) if x1<x2x_1 < x_2

(B) x1,x2∈[a,b],f(x1)≥f(x2)x_1, x_2 \in [a, b], f(x_1) \geq f(x_2) if x1>x2x_1 > x_2

(C) (A) x1,x2∈[a,b],f(x1)≤f(x2)x_1, x_2 \in [a, b], f(x_1) \leq f(x_2) if x1<x2x_1 < x_2

(D) (A) x1,x2∈[a,b],f(x1)<f(x2)x_1, x_2 \in [a, b], f(x_1) < f(x_2) if x1>x2x_1 > x_2

Solution

✅ Correct Option: 3

A function is (non-strictly) increasing on [a,b] iff for x1<x2x_1 < x_2, f(x1)≤f(x2)f(x_1) \leq f(x_2).

Statement A: f(x1)≥f(x2)f(x_1) \geq f(x_2) when x1<x2x_1 < x_2 describes decreasing - WRONG.

Statement B: f(x1)≥f(x2)f(x_1) \geq f(x_2) when x1>x2x_1 > x_2 - CORRECT (larger input gives larger output).

Statement C: f(x1)≤f(x2)f(x_1) \leq f(x_2) when x1<x2x_1 < x_2 - CORRECT (standard form).

Statement D: describes decreasing - WRONG.

B and C are correct.

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