View Full Version : straight line question

10-26-2013, 04:27 AM
A straight line (l) has equation -5y=4-2x , which of the following is the slope of a perpendicular line to line (l)?

(A) \frac{5}{2}

(B) \frac{2}{5}

(C) \frac{-5}{2}

(D) \frac{-2}{5}


10-26-2013, 04:28 AM
In order to find the slope of a line we must rewrite the equation to slope-intercept form i.e. y=ax+b where a is the slope.

So, the equation can be written as -5y=4-2x \Rightarrow y=\frac{2}{5}x-\frac{4}{5}

Thus the slope of line (l) is m_{l}=\frac{2}{5}.

The slope m_{k} of a perpendicular line to line (l) must be satisfy the following equation

m_{k} m_{l}=-1 \Rightarrow m_{k}=\frac{-5}{2}

Therefore the correct answer is (C).

Hope these help!!:)

10-26-2013, 04:28 AM
Thank you!!:)