Solve the following set of simultaneous equations: 3x + 2y = 15 & 9x + 4y = 1

Label your equations 1 and 2.
Look to eliminate one of your variables to create a third equation with only one variable.
To do this multiply the first equation by 2 to obtain: 6x + 4y =30 *Label as equation 3
Now both equation 2 and 3 contain the term 4y, which means we are now able to eliminate y from the set of equations.
Subtract equation 3 from equation 1 to obtain -3x = 29.
Rearrange to find the value of x by diving both sides my -3, resulting in x = -29/3.
We have now found our x value. With this new information, we can input the x value into any of our 3 equations to obtain our y value. *Best to choose an equation which hasn't been manipulated
Substituting into equation 1 and rearranging we obtain y = 22.
We have now found the solutions which satisfy both our original equations. x = -29/3 & y = 22. *Check they are correct by substituting both values into one of the equations.

Answered by Chris A. • Maths tutor

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