Solve the simultaneous equations: 5x + y = 21, x - 3y = 9

Call '5x + y = 21' equation 1 and 'x - 3y = 9' equation 2. To solve this, we need the coefficients of x in both equations to be the same or the coefficients of y in both equations to be the same.
Method 1 - solving for y firstMultiply equation 2 by 5 to get:5x - 15y = 45 (call this equation 3)Now we are going to take equation 1 away from equation 3: 5x - 15y = 45 - 5x + y = 21 which becomes: -16y=24Solve for y:y=-24/16 =-3/2Sub this value into equation 1 to solve for x:5x + (-3/2) = 215x = 45/2x= 9/2

Answered by Basil I. Maths tutor

3809 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

Solve the simultaneous equations algebraically


A right angled triangle has sides of length 3 and length 4, what is the length of the hypotenuse?


f(x) = 2x^2 + 7x + 6 . factorize this equation


Expand and simplify: (2x – 3y)(5x + 2y)


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