Question

Solve the system by using elimination 3x+3y=-9 3x-3y=21

Answer 1

y=-5

x=2

Explanation:

3x + 3y=-9

3x - 3y=21

-

0+6y=-30

6y=-30

y=-5

3x-15=-9

x=2

Answer 2

`\large\boxed{x=2,\ y=-5\to(2,\ -5)}`

Explanation:

`\underline{+\left\{\begin{array}{ccc}3x+3y=-9\\3x-3y=21\end{array}\right}\qquad\text{add both sides of the equations}\\.\qquad\qquad6x=12\qquad\text{divide both sides by 6}\\.\qquad\qquad\boxed{x=2}\\\\\text{Put the value of x to the first equation}\\\\3(2)+3y=-9\\6+3y=-9\qquad\text{subtract 6 from both sides}\\3y=-15\qquad\text{divide both sides by 3}\\\boxed{y=-5}`