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  1. AP Calculus
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What is the limit definition of the derivative?

f′(x)=lim⁡h→0f(x+h)−f(x)hf'(x) = \lim_{h \to 0} \frac{f(x + h) - f(x)}{h}f′(x)=limh→0​hf(x+h)−f(x)​

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What is the limit definition of the derivative?

f′(x)=lim⁡h→0f(x+h)−f(x)hf'(x) = \lim_{h \to 0} \frac{f(x + h) - f(x)}{h}f′(x)=limh→0​hf(x+h)−f(x)​

What is the point-slope form of a line?

y−y1=m(x−x1)y - y_1 = m(x - x_1)y−y1​=m(x−x1​)

How do you find the slope (m) of a tangent line?

m=f′(x0)m = f'(x_0)m=f′(x0​), where x0x_0x0​ is the x-coordinate of the point of tangency.

How to find the equation of the tangent line?

  1. Find f′(x)f'(x)f′(x). 2. Evaluate f′(x0)f'(x_0)f′(x0​) to find the slope mmm. 3. Use point-slope form: y−f(x0)=m(x−x0)y - f(x_0) = m(x - x_0)y−f(x0​)=m(x−x0​).

How to find the derivative of f(x)=x2f(x) = x^2f(x)=x2 using the limit definition?

  1. Plug into the limit definition: lim⁡h→0(x+h)2−x2h\lim_{h \to 0} \frac{(x+h)^2 - x^2}{h}limh→0​h(x+h)2−x2​. 2. Expand: lim⁡h→0x2+2xh+h2−x2h\lim_{h \to 0} \frac{x^2 + 2xh + h^2 - x^2}{h}limh→0​hx2+2xh+h2−x2​. 3. Simplify: lim⁡h→02xh+h2h\lim_{h \to 0} \frac{2xh + h^2}{h}limh→0​h2xh+h2​. 4. Factor and cancel: lim⁡h→0(2x+h)\lim_{h \to 0} (2x + h)limh→0​(2x+h). 5. Evaluate the limit: 2x2x2x.

How to find the tangent line to f(x)=x2f(x) = x^2f(x)=x2 at x=1x = 1x=1?

  1. Find f′(x)f'(x)f′(x): f′(x)=2xf'(x) = 2xf′(x)=2x. 2. Find the slope at x=1x = 1x=1: f′(1)=2f'(1) = 2f′(1)=2. 3. Find the y-coordinate at x=1x = 1x=1: f(1)=1f(1) = 1f(1)=1. 4. Use point-slope form: y−1=2(x−1)y - 1 = 2(x - 1)y−1=2(x−1).

How to find where the tangent line is horizontal for f(x)=x3−3xf(x) = x^3 - 3xf(x)=x3−3x?

  1. Find f′(x)f'(x)f′(x): f′(x)=3x2−3f'(x) = 3x^2 - 3f′(x)=3x2−3. 2. Set f′(x)=0f'(x) = 0f′(x)=0: 3x2−3=03x^2 - 3 = 03x2−3=0. 3. Solve for xxx: x=±1x = \pm 1x=±1.

How to evaluate lim⁡h→01x+h−1xh\lim_{h \to 0} \frac{\frac{1}{x+h} - \frac{1}{x}}{h}limh→0​hx+h1​−x1​​?

  1. Find a common denominator: lim⁡h→0x−(x+h)x(x+h)h\lim_{h \to 0} \frac{\frac{x - (x+h)}{x(x+h)}}{h}limh→0​hx(x+h)x−(x+h)​​. 2. Simplify: lim⁡h→0−hx(x+h)h\lim_{h \to 0} \frac{\frac{-h}{x(x+h)}}{h}limh→0​hx(x+h)−h​​. 3. Multiply by the reciprocal: lim⁡h→0−hx(x+h)h\lim_{h \to 0} \frac{-h}{x(x+h)h}limh→0​x(x+h)h−h​. 4. Cancel hhh: lim⁡h→0−1x(x+h)\lim_{h \to 0} \frac{-1}{x(x+h)}limh→0​x(x+h)−1​. 5. Evaluate the limit: −1x2\frac{-1}{x^2}x2−1​.

How to find the derivative of y=3x2+4xy = 3x^2 + 4xy=3x2+4x using the limit definition?

  1. Plug into the limit definition: lim⁡h→0[3(x+h)2+4(x+h)]−[3x2+4x]h\lim_{h \to 0} \frac{[3(x+h)^2 + 4(x+h)] - [3x^2 + 4x]}{h}limh→0​h[3(x+h)2+4(x+h)]−[3x2+4x]​. 2. Expand: lim⁡h→03x2+6xh+3h2+4x+4h−3x2−4xh\lim_{h \to 0} \frac{3x^2 + 6xh + 3h^2 + 4x + 4h - 3x^2 - 4x}{h}limh→0​h3x2+6xh+3h2+4x+4h−3x2−4x​. 3. Simplify: lim⁡h→06xh+3h2+4hh\lim_{h \to 0} \frac{6xh + 3h^2 + 4h}{h}limh→0​h6xh+3h2+4h​. 4. Factor and cancel: lim⁡h→0(6x+3h+4)\lim_{h \to 0} (6x + 3h + 4)limh→0​(6x+3h+4). 5. Evaluate the limit: 6x+46x + 46x+4.

What does the graph of f′(x)>0f'(x) > 0f′(x)>0 tell us about f(x)f(x)f(x)?

f(x)f(x)f(x) is increasing.

What does the graph of f′(x)<0f'(x) < 0f′(x)<0 tell us about f(x)f(x)f(x)?

f(x)f(x)f(x) is decreasing.

What does the graph of f′(x)=0f'(x) = 0f′(x)=0 tell us about f(x)f(x)f(x)?

f(x)f(x)f(x) has a horizontal tangent, which could be a local max, local min, or a stationary point.

What does the graph of f′′(x)>0f''(x) > 0f′′(x)>0 tell us about f(x)f(x)f(x)?

f(x)f(x)f(x) is concave up.

What does the graph of f′′(x)<0f''(x) < 0f′′(x)<0 tell us about f(x)f(x)f(x)?

f(x)f(x)f(x) is concave down.

What does the graph of f(x)=cf(x) = cf(x)=c (a constant) tell us about f′(x)f'(x)f′(x)?

f′(x)=0f'(x) = 0f′(x)=0 (a horizontal line at y=0).

What does a sharp corner or cusp on the graph of f(x)f(x)f(x) tell us about f′(x)f'(x)f′(x)?

f′(x)f'(x)f′(x) does not exist at that point (non-differentiable).

If the graph of f(x)f(x)f(x) is a straight line, what is the graph of f′(x)f'(x)f′(x)?

The graph of f′(x)f'(x)f′(x) is a horizontal line, representing the constant slope of f(x)f(x)f(x).