Example 2 Find the equation of the tangent to the circle
x + y2 + 4x - 10y = 12 at the point (3, 1).

-5x + 4y = -11.

Step-by-step explanation:

If it's a circle then it must be x^2 not x.

x^2 + y^2 + 4x - 10y = 12

Using implicit differentiation:

2x + 2y y' + 4 - 10 y' = 0

y'( 2y - 10) = -2x - 4

y' = (-2x - 4)/(2y - 10)

y' = (-x - 2) / (y - 5) = the slope of the tangent.

At  (3, 1),  y' = (-3-2) / (1 - 5)

=  5/4.

So the required equation is

y - y1 = 5/4(x - x1)  where x1 = 3 and y1 = 1.

y - 1 = 5/4(x - 3)

y = 5/4(x - 3) + 1

Multiply through by 4:

4y = 5(x - 3) + 4

4y = 5x - 15 + 4

In standard form the equation is:

-5x + 4y = -11.

damm bro the struggle

step-by-step explanation: