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### How do you solve the following simultaneous equation?

2x - 6y = 18

4x + 3y = 6

First, make either the x or y the same value by multiplying the equations. Let's choose x.

2x - 6y = 18      x2

4x + 3y = 6       x1

(+)4x - 12y = 36

(+)4x + 3y = 6

Now, we use the rule of 'same sign subtract', 'different sign add'. As the signs are the same in this example, we will subtract the equations.

-15y = 30

Now, we must divide both sides by -15 in order to isolate the y.

y = 30/-15

y = -2

We must then substitute the value for y into one of the equations to find x.

4x + 3y = 6     (substitute y = -2)

4x + 3(-2) = 6

4x - 6 = 6

Now we must add 6 to both sides to get the 4x on its own.

4x = 12

Then divide both sides by 4 to find the value of x.

x = 12/4

x = 3

We can then check our values (x = 3, y = -2) are correct by substituting them into the other equation.

4x + 3y = 6     (substitute x = 3, y = -2)

4(3) + 3(-2) = 6

12 - 6 = 6

6 = 6

This means that we successfully solved the simultaneous equation.

2 years ago

Answered by Jason, a GCSE Maths tutor with MyTutor

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