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 first equation.

x + 6y + z = 2
x – 3y + 2z = –1
x + 5y + 3z = –4

Answer 1

Solve [1] for x:
x =-6y-z+2

Now sub it into [2] in place of x:
(-6y-z+2)-3y+2z=-1
-9y+z=-3 [2]'

Now sub it into [3] in place of x:
(-6y-z+2)+5y+3z=-4
-y+2z=-6 [3]'

The new 2x2 system would then be solved:
-9y+z=-3 [2]'
-y+2z=-6 [3]'

Your problem implies that this is the answer, not the actual solution to the 3x3 system.

Answer 2

thank you for your help..but are you sure??

Answer 3

well i have made arithmetic errors before; let me check it with wolfram

Answer 4

im gonna go with your answer...thnkx

Answer 5

the answer to the 3x3 is x=5, y=0, z=-3; the answer to the 2x2 is y=0 z=-3
yes I am sure