Question

If you were to use the substitution method to solve the following

system, choose the new equation after the expression equivalent to x
from the second equation is substituted into the first equation.
3x + 2y = -21
x-3y = 4 (6 points)

Answer 1

x = 4 , y = -3

Explanation:

To solve the system of equation using substitution method

we say let

3x + 2y = -21....................................... equation 1

x-3y = 4............................................ equation 2

from equation 2

x-3y = 4............................................ equation

x = 4 + 3y.....................................................................equation 3

substitute for equation 3 into equation 1

3x + 2y = -21....................................... equation 1

3(4+3y) + 2y = -21

12 + 9y +2y = -21

11y = -21 -12

11y = -33

divide both sides by the coefficient of y which is 11

11y/11 = -33/11

y = -3

put the value of y = -3 into equation 3

x = 4 + 3y.....................................................................equation 3

x = 4 + 3(-3)

x = 4 + 0

x = 4