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Question

Let f,g and h be functions from R to R. Show that
(i) (f+g)oh=foh+goh
(ii) (f.g)oh=(foh).(goh)

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Solution

(i)

To prove:

(f+g)oh=foh+goh

Consider:

((f+g)oh)(x)

=(f+g)(h(x))

=f(h(x))+g(h(x))

=(foh)(x)+(goh)(x)

=(foh)+(goh)(x)

((f+g)oh)(x)=(foh)+(goh)(x) for all xR

Hence, (f+g)oh=foh+goh

(ii)

To prove: (f.g)oh=(foh).(goh)

Consider:

((f.g)oh)(x)

=(f.g)(h(x))
=f(h(x)).g(h(x))
=(foh)(x).(goh)(x)
=(foh).(goh)(x)
((f.g)oh)(x)=(foh).(goh)(x) for allxR
Hence, (f.g)oh=(foh).(goh)

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