Posted by David on Monday, March 30, 2009 at 5:54pm.
Solve the system of equations: x - y - z = 2; x + 2y - 2z = 3; 3x - 2y - 4z = 5?
well, you have:
multiply both sides of the equation 1 by 2:
x-y-z=2 ===> 2x-2y-2z=4
add this by equation 2:
==> 3x - 4z = 7 (*)
now, multiple both sides of equation 1 by -2:
==> -2x + 2y + 2z = -4
add this by equation 3:
-2x + 2y + 2z = -4
===> x - 2z = 1
great. now you have
x - 2z = 1
3x - 4z = 7
so , multiple both sides of the first one by -2:
-2x + 4z = -2
3x - 4z = 7
===> (add them together) x = 5
3x - 4z = 7 ===(x=5)=> 15 - 4z = 7 ==> 4z = 8 ==> z=2
x-y-z= 2 ===> 5-y-2 = 2 ==> y=1
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