How do you solve simultaneous equations?

I will run through an example of how to solve a set of simultaneous equations. In simultaneous equations you are given two or more algebraic equations and you need to solve them for the variables, usually called x and y. You start off by trying to get equivalent coefficients for either the x or y value in both of the equations.  For example: (1) 4x + y = 24 and (2) 7x + 3y = 47. Here we can multiply equation (1) by 3 so that both the x coefficients are equal to 3. So 3*(1) is equivalent to 12x + 3y =72. Now we can subtract (2) from 3*(1). This gives 5x + 0y = 25, giving 5x = 25 therefore x = 5. Substituting x back into equation (1) we get 4*5 + y =24. So y = 24 - 20 and y = 4. Giving us the solutions: x=5 and y=4.

DH

Related Maths GCSE answers

All answers ▸

An triangular prism has base xcm, height (x+4)cm and length 4xcm. Find the volume of the prism in terms of x. Find the volume when x=2cm.


Consider an isosceles triangle ABC, where AB=AC=1, M is the midpoint of BC, and <BAM=<CAM=x. Use trigonometry to find an expression for BM and by finding BC^2, show that cos2x = 1 - 2(sinx)^2.


Solve the equation 3x^2 +17x -6 = 0 without using a calculator


Work out (2^34) / (2^3)^10