Write the point slope form of the equation of (1,-2), perpendicular to 4x+9y=-9

Question

What is the point slope form of the equation of (1,-2), perpendicular to 4x+9=-9 

Answer 1

To get the perpendicular line, we need the negative reciprocal of the slope. We see the 4 next to the x, so the original slope is 4. The negative reciprocal means we flip the numerator and denominator and switch positive-negative. That gives us -¼.

 

Here's the point-slope formula:

y - y₁ = m(x - x₁)

With a point given of (1, -2), we just put that into the formula:

y - -2 = -¼(x - 1)

y + 2 = -¼(x - 1)