Question

Explain what their first step would be if they wanted to eliminate the y variable from the equations.

Answer 1

• r1 +4×r3 ⇒ r1
• r2 -3×r3 ⇒ r2

Explanation:

We note that the coefficient of y in equation (iii) is 1, so it is convenient to use that equation to eliminate y from the others.

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To eliminate the y-variable from equation (i), four times equation (iii) can be added to equation (i).

To eliminate the y-variable from equation (ii), three times equation (iii) can be subtracted from equation (i).

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The result of these operations would be ...

`10x +6z = 28\quad\text{(iv)}\\\\-7x-9z=2\quad\text{(v)}`