Solve the simultaneous equations: 5x + 3y = 9 and 7x - 2y = 25.

To solve these similar equations, we must either first eliminate x or y. There are multiple ways of doing this, one being rearranging one of the equations so that it is either "x=.." or "y=..." and then substituting the rearranged equation into the other equation and so eliminating one variable. 

Specifically for this example it could be:

Rearrange 7x - 2y = 25 to 2y = 7x - 25. Then divide the entire equation by 2, giving: y = (7/2)x - (25/2). 

Now enter this new equation into the second equation in place of y and solve for x: 5x + 3y = 9 becomes 5x+3(3.5x - 12.5) = 9. Rearrange by first expanding the brackets and collecting all x on one side and then dividing by the coefficient of x to give x = 3.

Now enter this into an equation and solve for y. For instance: 5x + 3y = 9, set x=3 giving 5(3) + 3y = 9. 3y=(-6) Y=(-2) 

you can check this but entering both these values for x and y into the second equation for example. 7(3)-2(-2)= 25

21- (-4) = 25. Therefore this is the correct solution. 

Answered by Màiri G. Maths tutor

10178 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

Solve this pair of simultaneous equations (1) 5x+2y=20 and (2) x+4y=13


3/5 of a number is 162. what is the number?


Solve the simultaneous equations 3x + 2y = 12 and 10y = 7x + 16


What is 45% of 60?


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