Q. Let f(x)=xex+exx+1 when x=−1.f is continuous for all real numbers.Find f(−1).Choose 1 answer:(A) e(B) 2(C) 1(D) −2e
Finding f(−1): We need to find the value of f(−1). However, we cannot directly substitute x=−1 into the function because the function is not defined at x=−1. We will use the limit process to find the value of f(x) as x approaches −1.
Using the limit process: Let's consider the limit of f(x) as x approaches −1:x→−1limf(x)=x→−1limxex+exx+1
Applying L'Hôpital's Rule: We can see that if we substitute x=−1 directly, we get 0/0, which is an indeterminate form. To resolve this, we can apply L'Hôpital's Rule, which states that if the limit of f(x)/g(x) as x approaches a value c is an indeterminate form 0/0 or ∞/∞, then the limit is the same as the limit of the derivatives of the numerator and the denominator, provided that the limit exists.
Finding the derivatives: We will find the derivatives of the numerator and the denominator separately. The derivative of the numerator x+1 with respect to x is 1. The derivative of the denominator xex+ex with respect to x is ex+xex+ex using the product rule and the fact that the derivative of ex is ex.
Substituting x=−1: Now we apply L'Hôpital's Rule:limx→−1f(x)=limx→−1ex+xex+ex1
Simplifying the expression: We substitute x=−1 into the derivatives to find the limit: x→−1limex+xex+ex1=e−1+(−1)e−1+e−11
Final result: Simplify the expression:(1)/(e−1−e−1+e−1)=(1)/(e−1)
Final result: Simplify the expression:(1)/(e−1−e−1+e−1)=(1)/(e−1)Since e−1 is the same as 1/e, we can rewrite the expression as:(1)/(1/e)=e