Question

Solve, using the substitution method.

y – 3x = 7
21 + 9x = 3y

(Points : 1)
There is no solution.
There are an infinite number of solutions.
The solution is (1, 10)
The solution is (28, 0)
help

Answer 1

send screen shot of question

Answer 2

y – 3x = 7
21 + 9x = 3y

Answer 3

x = 3 , y = 2

Answer 4

wait no

Answer 5

lol , take your time. i have another one like this problem there really confusing to me

Answer 6

y – 3x = 7
y = 7 + 3x

Plug in this y in the 2nd equation:

21 + 9x = 3(7 + 3x)
21 + 9x = 21 + 9x
21 - 21 = 9x - 9x
0 = 0

When you encounter this situation, the 2nd equation is just a multiple of the 1st equation, and is therefore the same line. So there are infinitely many solutions (both lines are lying on top of each other)