Question 1198735: Find the equation of the line perpedicular to x-4y=3 and passes through the point (2,10) Found 4 solutions by Theo, MathTherapy, josgarithmetic, greenestamps:Answer by Theo(13342) (Show Source): You can put this solution on YOUR website! slope intercept of the straight line equation is y = mx + b
your equation is x - 4y = 3
add 4y to both sides of the equation and subtract 3 from both sides of the equation to get x - 3 = 4y
divide both sides of the equation by 4 to get x/4 - 3/4 = y
switch sides on the equation to get y = x/4 - 3/4
this is the same as y = 1/4 * x - 3/4
a line perpendicular to the line of this equation is has a slope that is a negative reciprocal of the line.
that would be a slope of -4
the line perpendicular to the given line is therefore y = -4 * x - 3/4
the more general form of that equation is y = -4 * x + b
to find the equation of that line that passes through the point (2,10), replace x with 2 and y with 10 to get 10 = -4 * 2 + b
simplify to get 10 = -8 + b
add 8 to both sides of that equation to get 18 = b
the equation of the line perpendicular to the given line and passing through the point (2,10) is y = -4 * x + 18
here's a graph of both lines.
the red line is the original line.
the blue line is the line perpendicular to it.
For an elementary solution, do what two of the other tutors do:
Put the given equation in slope-intercept form to find the slope;
Find the slope of the perpendicular line, which is the negative reciprocal of the slope of the given line; and
Use that slope and the given point with either the slope-intercept or standard form of a linear equation to find the equation.
Students with knowledge of only basic algebra should know that solution method.
For an easier solution, for students with a more extensive knowledge of math, do what tutor @MathTherapy does.
Given a linear equation in standard form Ax+By=C, the equation of a line perpendicular to the given line is of the form Bx-Ay=D (switch the coefficients and change the sign of one of them).
Then just plug in the coordinates of the given point to find the answer.