Solution
Related Formula
A function is one-one if its derivative is strictly monotonic (always positive or always negative) across its domain. It is onto if its range equals its co-domain.
Core Logic
Rewrite the function by multiplying the numerator and denominator by 2^x:
f(x) = 22x - 122x + 1 = 1 - 222x + 1Step 1: Check One-One property
Differentiating f(x) with respect to x :
f'(x) = 2(22x + 1)² · 2 · 22x · ln 2 = 4 · 22x · ln 2(22x + 1)²Since 22x > 0 and ln 2 > 0, f'(x) > 0 always. Thus, f(x) is strictly increasing, confirming it is a one-one function.
Step 2: Check Onto property
Analyze the limits at boundaries:
x → -∞ f(x) = 1 - (2)/(0 + 1) = -1 x → ∞ f(x) = 1 - 0 = 1Thus, the range of the function is (-1, 1). Since the given co-domain is (-∞, 1) and Range ≠ Co-domain , the function is not onto.
Pattern Recognition
The expression given is a shifted form of the hyperbolic tangent function (x ln 2). Hyperbolic tangent always maps to (-1, 1), making its restriction against (-∞, 1) non-surjective (not onto).
Chapter Mix
Class 12 Mathematics: Relations and Functions