If you were to use the substitution method to solve the following system, choose the new system of equations that would result if x was isolated in the second equation.

2x - 3y - z = -1
x - 4y + 3z = -11
2x + 9y + 3z = -13

A. -11y + 5z = 21
y + 9z = 9
B. 5y - 7z = 21
17y - 3z = 9
C. 7x - 13y = -14
8x + 0y = -16
D. -5x +5y = -8
-4x + 18z = -10

Question

If you were to use the substitution method to solve the following system, choose the new system of equations that would result if x was isolated in the second equation.

2x - 3y - z = -1
x - 4y + 3z = -11
2x + 9y + 3z = -13

	 A. -11y + 5z = 21
y + 9z = 9	
	 B. 5y - 7z = 21
17y - 3z = 9	
	 C. 7x - 13y = -14
8x + 0y = -16	
	 D. -5x +5y = -8
-4x + 18z = -10

anonymous · Answer

@texaschic101

anonymous · Answer

@texaschic101 can you help me with this?

texaschic101 · Answer

x - 4y + 3z = -11
x = 4y - 3z - 11

2x - 3y - z = -1
2(4y - 3z - 11) - 3y - z = -1
8y - 6z - 22 - 3y - z = -1
5y - 7z = 21 <==== here is one new equation

2x + 9y + 3z = -13
2(4y - 3z - 11) + 9y + 3z = -13
8y - 6z - 22 + 9y + 3z = -13
17y - 3z = 9 <==== here is the other new equation

answer is B

texaschic101 · Answer

I just isolated x in the second equation and subbed that in for x in the other equations, and I just simplified the equations