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

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

anonymous · Answer

find x in terms of y and z from first equation
2x = -1 + 3y + z
x =  (-1 + 3y + z)/2

anonymous · Answer

Now put this value of x in second equation

Would you like to do it @lornbeach

whpalmer4 · Answer

Well, to isolate $x$ in the second equation, I would add $4y-3z$ to both sides, giving
$$x=4y-3z-11$$

Now substitute $4y-3z-11$ wherever we encounter $x$ in the other two equations:

$$2(4y-3z-11) - 3y-z = -1$$$$2(4y-3z-11)+9y+3z=-13$$

After distributing and collecting like terms, that would be:

$$5y-7z=21$$$$17y-3z=9$$