How to solve a simultaneous equation?

In simultaneous equations, at this level, you are often given two equations both containing an x and a y. For example:Equation1: y + 2x = 3Equation2: 4y + 2x = 8.The first step in approaching this is to try re-arrange one equation with either just y or just x on the left hand side and everything else on the right. Let's rearrange equation 1.We want the equation to read "y =" to do this we need to move "+2x" over to the right hand side. Remember when moving across the equals sign the -/+ sign changes.Our equation now becomes y = 3 - 2xGreat! Now we are almost ready to sub this equation into equation 2! But first note that equation 2 can be simplified further. If we divide through by 2 then we have a simpler equation to solve.. it becomes 2y + x = 4.Now lets put our first equation into this one (substitute in where ever you see y)Joining them together we now get 2(3-2x) + x = 4. Simplyfing this we get, 6 - 4x + x = 4. Then, 2 = 3x.We can use this to find a value for x! lets divide by 3. We now have that x = 2/3.Now that we have solved for one value, we can find the other. To find y, we must put our new value for x into either equation. Let's try it with the first one. y = 3 - 2(2/3). This gives us, y = 3 - (4/3) which is 5/3. (roughly 1.667).If you wanted to be sure of your answers, you can sub them into the other equation and make sure it works!

Answered by Sophie B. Maths tutor

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