1.

Let R+ be the set of all non- negative real numbers. Show that the function f: R+ → [4,∞) given by f(x) = x2 + 4 is invertible and write the inverse of f.

Answer»

f(x1) = f(x2

X12 + 4 = X22 + 4 

x1 = x2 

∴ f (x) is one-one 

Let y = f(x) y = 4x + 3 

x = y - 3/4 ∈R+ 

∴ f (x) is onto 

Let f-1 (x) = y 

f(y) = x 

4y +3 = x

y = x - 3/4 

∴ f-1 : [4,8) → R+ is defined by 

f-1 (x) = x - 3/4



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