Two lines are perpendicular when the product of their gradients equal to -1. So:
m₁ * m₂ = -1
Let's get the first equation in gradient-intercept form (same as equation two).
2x + 3y = 4
3y = -2x + 4
y = -⅔x + ⁴⁄₃
We know the first gradient, and now we can find the gradient of the second line (which when multiplied will result in -1 as these lines are perpendicular). So:
