Solve the simultaneous equation- 2x+8y=10 and 3x+2y=5

Firstly, lets name each equation A and B- this will help us later. If I told you what x was, you would be able to use either equation to find y- easy! so lets first find one unknown (x or y) then use that to find the other unknown! Now there are two easy ways to do this and your exam board/ test paper may want you to do this in a way specified. Lets start with my personal preference because of ease! Lets start with A, what we want to do is get our x on its own so we can then sub it into our B equation therefore eliminating 'x' leaving us with just the y terms. So lets put our terms that arent x terms to the right so now we have 2x=10-8y, now divide everything by 2 and we have x=5-4y This is our new version of A lets call it A'. Now we can sub A' into B for the 'x'. B is now 3(5-4y) + 2y = 5. If we simplify this by first expanding the brackets 15-12y+2y=5 and then collect our y terms on one side and numbers on the other we have 10y=10 so of course y=1. Now we can sub this y value into A or B (preferably both to check) if we do this to A we have 2x+8(1)=10 giving x=1. Our solution is now x=1 y=1 ! The second way to do this is to compare A and B and see if we can add or subtract a multiple of A or B to the other in order to eliminate x or y. If we multiply B by 4 we get 12x+8y=20 now we see in equation A we have '8y' in there. If we subtract our A from 4B we get 10x+0=10 so obviously x=1 again. If we once again sub this value into both A and B we will get y=1 like we did the first time. We can use 4B because we are multiplying both the LHS of the equation and the RHS so the equation is kept in tact! I hope this helped enough to reuse and apply this to different equations similar to this one, prepare for fractions and negatives aswell!

Answered by Max G. Maths tutor

4332 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

If x:y=7:4 and x + y = 88, work out the value of x – y.


How do you differentiate x^x?


P is a point on a circle with the equation x^2 + y^2 = 45. P has x-coordinate 3 and is above the x axis. Work out the equation of the tangent to the circle at point P.


Write x^2+6x+14 in the form of (x+a)^2+b where a and b are constants to be determined.


We're here to help

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