4x - 9y = - 21

- 4x - 3y = 9

(-3,1)

y = 1

x = - 3

Step-by-step explanation:

4x-9y=-21

-4x-3y=9

solve the equation

4x=-21+9y

-4x-3y=9

substitute the value of 4x onto an equation

-1 (-21+9y) - 3y=9

multiply - 1 to the numbers in parenthesis

-21+-9-3y=9

add - 9 to 9 and put the negative on nine as a positive.

-21-3y=18

add - 21 to 18 but since 21 is a negative the equation is subtraction.

-3y=-3

divide Both sides by - 3

y=1

substitute the value of y into an equation

-4x-3•1=9

multiply 3 to 1

-4x-3=9

put - 3 as a positive and add 3 to 9

-4x=12

divide both sides by - 4

x = - 3

(-3,1)