MHB 217 AP Calculus Exam continous function with k

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The function f(x) is defined piecewise, with a specific value k at x=2 and a rational expression for x not equal to 2. For f(x) to be continuous at x=2, three conditions must be met: f(2) must be defined, the limit as x approaches 2 must exist, and the limit must equal f(2). The limit as x approaches 2 is calculated to be 5, which means k must also equal 5 for continuity. Therefore, the correct value of k for the function to remain continuous at x=2 is 5.
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$f(x)=\begin{cases}
\dfrac{(2x+1)(x-2)}{x-2}, &\text{for } x\ne 2 \\[3pt]
k, &\text{for } x=2 \\
\end{cases}$$(A)\,0\quad(B)\,1\quad(C)\,2\quad(D)\,3\quad(E)\,5\quad$

ok not sure if this the standard way to do this but
$x-2$ will cancel out
then if $x=2$ for $2(2)+1 = 5$ which is (E)
 
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Re: 217 AP Caluclus Exam continuous function with k

A function $f(x)$ is continuous at $x=c$ if ...

1. $f(c)$ is defined.

2. $$\lim_{x \to c} f(x)$$ exists.

3. $$ \lim_{x \to c} f(x)= f(c)$$$f(2) = k$ is defined

$$\lim_{x \to 2} f(x) = 2x+1$$ exists.

$$\lim_{x \to 2} f(x) = 2(2)+1 = 5 = k$$
 
Thanks I'll add that to the MeWe post
 
There are probably loads of proofs of this online, but I do not want to cheat. Here is my attempt: Convexity says that $$f(\lambda a + (1-\lambda)b) \leq \lambda f(a) + (1-\lambda) f(b)$$ $$f(b + \lambda(a-b)) \leq f(b) + \lambda (f(a) - f(b))$$ We know from the intermediate value theorem that there exists a ##c \in (b,a)## such that $$\frac{f(a) - f(b)}{a-b} = f'(c).$$ Hence $$f(b + \lambda(a-b)) \leq f(b) + \lambda (a - b) f'(c))$$ $$\frac{f(b + \lambda(a-b)) - f(b)}{\lambda(a-b)}...

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