Question

Which equation represents a line which is perpendicular to the line 4y - 3x = -20?

Answer 1

Remember that when two lines are perpendicular, the product of their slopes is equal to -1.

The slope-intercept form of the equation of a line with slope m and y-intercept b is:

$y=mx+b$

Isolate y from the given equation to find the slope of the line:

$\begin{gathered} 4y-3x=-20 \\ \Rightarrow4y=3x-20 \\ \Rightarrow y=\frac{3x-20}{4} \\ \Rightarrow y=\frac{3}{4}x-5 \end{gathered}$

Then, the slope of the given line is 3/4. For a line with slope m to be perpendicular to it, m must satisfy the following condition: