Find the equation of the tangent line to f(x) = x^2 + 2x at x = 1.
Solution
Problem
Find the equation of the tangent line to f(x) = x^2 + 2x at x = 1.
Step 1: Find the point on the curve.
The function is:
f(x) = x^2 + 2x
Evaluate f(1):
f(1) = 1^2 + 2(1)
f(1) = 1 + 2
f(1) = 3
So the tangent line passes through the point (1, 3).
Step 2: Find the derivative.
Differentiate:
f'(x) = 2x + 2
The derivative gives the slope of the tangent line at any x-value.
Step 3: Find the slope at x = 1.
f'(1) = 2(1) + 2
f'(1) = 4
So the tangent line has slope 4.
Step 4: Use point-slope form.
The point-slope equation is:
y - y1 = m(x - x1)
Substitute m = 4 and the point (1, 3):
y - 3 = 4(x - 1)
Step 5: Simplify.
y - 3 = 4x - 4
y = 4x - 1
Therefore, the equation of the tangent line is y = 4x - 1.
Result
y = 4x - 1