Math  /  Calculus

QuestionLet h(x)=e2xx3h(x)=\frac{e^{2 x}}{x-3} Where does hh have critical points?

Studdy Solution

STEP 1

What is this asking? Where does the slope of e2xx3\frac{e^{2x}}{x-3} equal **zero** or become **undefined**? Watch out! Remember a fraction is **undefined** when the **denominator** is zero, and don't forget the **chain rule**!

STEP 2

1. Define the function and its derivative
2. Find where the derivative is zero
3. Find where the derivative is undefined

STEP 3

Let's call our function h(x)h(x).
It's defined as: h(x)=e2xx3h(x) = \frac{e^{2x}}{x-3}

STEP 4

To find the **critical points**, we need the **derivative**!
We'll use the **quotient rule**: ddx(f(x)g(x))=f(x)g(x)f(x)g(x)[g(x)]2\frac{d}{dx}\left(\frac{f(x)}{g(x)}\right) = \frac{f'(x)g(x) - f(x)g'(x)}{[g(x)]^2} In our case, f(x)=e2xf(x) = e^{2x} and g(x)=x3g(x) = x - 3.
So, f(x)=2e2xf'(x) = 2e^{2x} (using the **chain rule**) and g(x)=1g'(x) = 1.

STEP 5

Plugging everything into the **quotient rule**: h(x)=2e2x(x3)e2x(1)(x3)2h'(x) = \frac{2e^{2x}(x-3) - e^{2x}(1)}{(x-3)^2} We can simplify by factoring out e2xe^{2x}: h(x)=e2x(2(x3)1)(x3)2=e2x(2x61)(x3)2=e2x(2x7)(x3)2h'(x) = \frac{e^{2x}(2(x-3) - 1)}{(x-3)^2} = \frac{e^{2x}(2x - 6 - 1)}{(x-3)^2} = \frac{e^{2x}(2x - 7)}{(x-3)^2} So, the derivative is h(x)=e2x(2x7)(x3)2h'(x) = \frac{e^{2x}(2x - 7)}{(x-3)^2}.

STEP 6

A fraction is zero only when its **numerator** is zero: e2x(2x7)=0e^{2x}(2x - 7) = 0 Since e2xe^{2x} is *always* positive (never zero), we only need to solve: 2x7=02x - 7 = 0

STEP 7

Adding **7** to both sides gives 2x=72x = 7.
Dividing both sides by **2** gives x=72x = \frac{7}{2}.

STEP 8

h(x)h'(x) is undefined when the **denominator** is zero: (x3)2=0(x-3)^2 = 0

STEP 9

Taking the square root of both sides gives x3=0x - 3 = 0, so x=3x = 3.

STEP 10

The **critical points** of h(x)h(x) are at x=72x = \frac{7}{2} (where the derivative is **zero**) and x=3x = 3 (where the derivative is **undefined**).

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