1.

If A = {1, 2, 3, 4}, B = {3, 5, 7, 9}, C = {7, 23, 47, 79} and f: A → B, g : B → C such that f(x) = 2x + 1 and g(x) = x2 – 2, then find (gof)-1 and f-1og-1 in ordered form.

Answer»

A = {1, 2, 3, 4}, B = {3, 5, 7,9} and

C = {7, 23, 47, 79}

f : A → B, f (x) = 2x + 1

g : B → C, g(x) = x2 – 2

Now, gof (x)=g{f(x)} = g(2x + 1)

= (2x + 1)2 – 2 = 4x2 + 4x – 1

∴ gof (x) = 4x2 + 4x – 1

On putting x = 1, 2, 3, 4

gof = {(1,7), (2, 23), (3,47),(4, 79)}

∵ gof is bijection function.

∴ Its inverse is possible

⇒ (gof)-1 = {(7, 1), (23, 2), (47,3), (79,4)}

⇒ f-1og-1 = {(7,1), (23, 2) (47, 3), (79,4)}

∵ (gof)-1 = f-1og-1 by theorem.



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