Question

Elimination/subtraction

Answer 1

Answer:

x = 0, y = 7

Step-by-step explanation:

Solving a system of equations using substitution requires one side to be equal to a variable present in the equation, in this case x or y. We should simplify the equation using elimination before substituting to reduce the chance of error.

In order to use the elimination method, you have to create variables that have the same coefficient—then you can eliminate them. These equations arew already aligned for us.

                  3x - 10y=-70

             -   4x +9y = 63

                  -x + y = 7

Now, for substitution, the equation must be set to a variable.

                  -x + y = 7

                  y = x + 7

Next, plug the equation in where applicable in another equation.

                  4x +9(x + 7) = 63

                  4x + 9x + 63 = 63

                  13x = 0

                  x = 0

The final step of substitution is to plug the known variable into an equation to find the other variable.

                  3(0) - 10y=-70

                  0 - 10y = -70

                  10y = 70

                  y = 7

I guarantee you this answer is correct, I worked it out using other methods and graphing prior to submitting this answer.

Answer 2

Answer:

x = 0 , y = 7

Step-by-step explanation:

$3x - 10y = - 70..............(1) \\ 4x + 9y = 63...................(2) \\ (1) \times 4 \\ 12x - 40y = - 280...........(3) \\ (2) \times 3 \\ 12x + 27y = 189...........(4) \\ (4) - (3) \\ 67y = 469 \\ \\ y = \frac{469}{67} \\ y = 7 \\ put \: y = 7 \: into \: (1) \\ 3x - 10(7) = - 70 \\ 3x - 70 = - 70 \\ 3x = - 70 + 70 \\ 3x = 0 \\ x = \frac{0}{3} \\ x = 0$