QUESTION IMAGE
Question
- find the equation of the tangent line to the graph of $f(x)=4 - x^{2}$ at the points (-1,3)
Step1: Find the derivative of the function
The derivative of $f(x)=4 - x^{2}$ using the power - rule $(x^n)'=nx^{n - 1}$ is $f'(x)=-2x$.
Step2: Evaluate the derivative at the given x - value
Substitute $x=-1$ into $f'(x)$. So $f'(-1)=-2\times(-1) = 2$. The value of the derivative at $x = - 1$ is the slope $m$ of the tangent line, so $m = 2$.
Step3: Use the point - slope form of a line
The point - slope form is $y - y_1=m(x - x_1)$, where $(x_1,y_1)=(-1,3)$ and $m = 2$.
Substitute these values: $y - 3=2(x+1)$.
Step4: Simplify the equation
Expand the right - hand side: $y - 3=2x + 2$.
Add 3 to both sides to get the equation in slope - intercept form: $y=2x+5$.
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$y = 2x + 5$