Solution
Related Formula
For a limit of 1∞ form, x → a [g(x)]h(x) equals:
e^ x → a h(x)[g(x) - 1]Core Logic
Let T = x → 1 ( (f(x + 2))/(f(3)) )(18)/((x - 1)²). As x → 1, (f(x+2))/(f(3)) → (f(3))/(f(3)) = 1. The exponent goes to ∞. This is a standard 1∞ form.
T = e^ x → 1 (18)/((x - 1)²) ( (f(x + 2) - f(3))/(f(3)) )Step 1: Simplify Exponent Limit
Given f(3) = 18:
T = e^ x → 1 (18)/((x - 1)²) ( (f(x + 2) - f(3))/(18) ) T = e^ x → 1 (f(x + 2) - f(3))/((x - 1)²)This is a (0)/(0) form limit.
Step 2: Apply L'Hopital's Rule
Differentiate numerator and denominator w.r.t x:
T = e^ x → 1 (f'(x + 2))/(2(x - 1))This is still a (0)/(0) form since f'(3) = 0. Apply L'Hopital's Rule again:
T = e^ x → 1 (f''(x + 2))/(2)Substitute x = 1:
T = e(f''(3))/(2)Step 3: Final Calculation
Given f''(3) = 4:
T = e(4)/(2) = e²The question asks for ₑ(T):
ₑ(T) = ₑ(e²) = 2Pattern Recognition
When expanding f(x) around an extrema (f'(a)=0) inside a 1∞ limit form, double L'Hopital isolates the second derivative divided by the Taylor factorial (2! = 2). The limit elegantly shrinks directly to f''(a)/2.
Chapter Mix
Class 11 Maths: Limits and Derivatives Class 12 Maths: Limits, Continuity and Differentiability