How do you solve the following simultaneous equations? 4x-3y=18, 7x+5y=52

First, we need to try and eliminate one of the x or the y variables from both equations. Here, we are going to eliminate the y variable. In order to do this, we need to make the y coefficients equal in both equations, and we can do this by multiplying the first equation through by 5 and the second one through by 3, so that both y variables are equal to 15. We get:

20x-15y=90 21x+15y=156

If we add the two equations together, we will eliminate the y variable, as required, because -15+15=0. Hence, we are left with one equation in terms of x:

41x=246, so x=6.

We can substitute this result into the first equation to get: 120-15y=90, and we can solve this to get y=2.

Hence, the solution to the simultaneous equations is x=6 and y=2.

AO

Related Maths GCSE answers

All answers ▸

How do I find the equation of a line between two points?


A 4 pint bottle of milk costs £1.18 A 6 pint bottle of milk costs £1.74 Which bottle of milk is the best value for money? You must show all your working.


A circle with centre C has equation x^2 + y^2 + 2x - 6y - 40 = 0. Express as (x - a)^2 + (y - b)^2 = d.


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