# Question

For each of the following functions, use the test given in Appendix 2 to determine whether it is convex, concave, or neither.

(a) f (x) = x1x2 – x21 – x22

(b) f (x) = 3x1 + 2x21 + 4x2 + x22 – 2x1x2

(c) f (x) = x21 + 3x1x2 + 2x22

(d) f (x) = 20x1 + 10x2

(e) f (x) = x1x2

(a) f (x) = x1x2 – x21 – x22

(b) f (x) = 3x1 + 2x21 + 4x2 + x22 – 2x1x2

(c) f (x) = x21 + 3x1x2 + 2x22

(d) f (x) = 20x1 + 10x2

(e) f (x) = x1x2

## Answer to relevant Questions

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