Question

The equation of line WX is 2x + y = -5. What is the equation of a line perpendicular to line WX in slope-intercept form that contains point (-1, -2)?

Answer 1

Answer:

The third choice is the one you want

Step-by-step explanation:

If we are to write the equation of a line perpendicular to WX, we first must determine what the slope of the WX is, because the line perpendicular to WX has a slope that is the flip of the slope of WX with the opposite sign.  Solving for y takes care of finding the slope of WX:

2x + y = -5 so

y = -2x - 5

The slope is -2.  That means that the reciprocal slope is 1/2.  Using that slope along with the coordinates x = -1 and y = -2, we first write the line using point-slope form and then solve it for y.  Start by filling in the m, the x value and the y value:

$y - (-2) = \frac{1}{2}(x-(-1))$

Getting rid of the double negatives gives us:

$y+2=\frac{1}{2}(x+1)$

Distributing then gives us:

$y+2=\frac{1}{2}x+\frac{1}{2}$

And finally solving for y (I am going to express the 2 on the left as 4/2 when I move it by subtraction in order to add those fractions):

$y=\frac{1}{2}x+\frac{1}{2}-\frac{4}{2}$

And the final equation in slope-intercept form is:

$y=\frac{1}{2}x-\frac{3}{2}$