Question

Choose a method to solve the following system of equations. Explain why you chose that method.

Solve.

y = 2x + 7

y = -2x - 5

Answer 1

Y=2 addition because the X’s cancel out

Answer 2

Explanation:

The given simultaneous equations are expressed as

y = 2x + 7 - - - - - - - - - -1

y = -2x - 5 - - - - - - - - - - 2

We would apply the method of substitution.

The first step is to equate equation 1 to equation 2. It becomes

2x + 7 = - 2x - 5

Next step is to add 2x to the left hand side and the right hand side of the equation. It becomes

2x + 2x + 7 = - 2x - 2x - 5

4x + 7 = - 5

Next step is to subtract 7 from the left hand side and the right hand side of the equation. It becomes

4x + 7 - 7 = - 5 - 7

4x = - 12

Next step is to divide the left hand side and the right hand side of the equation by 4. It becomes

4x/4 = -12/4

x = - 3

Substituting x = - 3 into equation 1, it becomes

y = 2 × - 3 + 7 = - 6 + 7

y = 1