Question

— 3х + 9y = — 21 — 3х +8y = -18 find the solution by system of equations

Answer 1

Answer:

x = -2

y = -3

Step-by-step explanation:

There are three methods for solving system of equations: elimination, substitution, and graphing. In this case elimination would be the best method since you have -3x for both equations. When solving by elimination, your goal is to eliminate one of the variables, in this case we will eliminate x. Subtract the bottom equation from the top (it is important to remember here that the negative will distribute to the entire equation).

-3х + 9y = -21

- (- 3х +8y = -18)

_____________

y = -3

Now plug this y-value in to either equation and solve for x

-3х + 9y = -21

-3х + 9(-3) = -21

-3x - 27 = -21

-3x = 6

x = -2

Check your answer by plugging both values in to the second equation

- 3х +8y = -18

- 3(-2) +8(-3) = -18

6 - 24 = -18

-18 = -18

Answer 2

Answer:

x=-2,y=-3

Step-by-step explanation:

x=7+3x

-3x+8y=-18

-21-y=-18

x=7+3x

y=-3

x=7+3x

x=-2

y=-3