How do I find the equation of a line that's perpendicular to another one?

Remember that the equation of a line is y=mx+c and m is the gradient of the line. The gradient of a perpendicular line will be the negative reciprocal of m ( that just means it will be -1/m). You can then use any other information you've been given in the question to substitute into the equation y=mx+c to get your answer. Let's have a look at an example so you can see how it works:So we have the line y=4x+2 and you want to find the perpendicular line to that which passes through the point (8,1) . The gradient of this line is 4 so the gradient of the perpendicular line will be -1/4 so you have y=-1/4x+c. Now you want to find c. But look, you also have a value for x, 8 and a value for y, 1 so substitute those into your y=mx+c equation. 1=(-1/4)(8)+c and rearrange to find c=3. Pop that into your equation and you get an answer of y=-1/4x+3

Answered by Verity P. Maths tutor

2770 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

Expand 5(2x-6)


There are a collection of CDs. There are 2 Rock CDs, x Pop CDs and 2x + 5 Jazz CDs. A CD is chosen at random, the probability that it is Rock is 1/20. Work out the probability it is Jazz.


The diameter of a circle is 14cm, work out its area


how do i factorise a quadratic equation when the coefficient of x^2 is not 1?


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2024

Terms & Conditions|Privacy Policy
Cookie Preferences