tangent of x^2 at a
Find the tangent at x = a
Let's perform the differentiation: ddx(x2)
ⓘ The derivative of x^n is n*x^(n-1): ddx(x2) = 2x
2x
Compute f(a)
The point of tangency is (a, a2)
Compute f'(a)
The slope is f'(a) = 2a
The tangent passes through this point with this slope: y = 2a·(x -a) + a2
Compute the y-intercept: b = a2 -2a·a
a2 -2a·a
ⓘ Multiplying powers with the same base adds the exponents: a·a = a2
a2 -2a2
ⓘ Like terms are grouped by adding their coefficients: a2 -2a2 = -a2
-a2
▶Tangent line:   y = 2ax -a2