Question 1118807
Multiply eq. 2 by 2 and subtract from eq. 1,
{{{x+2y+2z-4x-2y-2z=1-4}}}
{{{-3x=-3}}}
{{{x=1}}}
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Subtract eq. 3 from eq. 1,
{{{x+2y+2z-3x-2y-2z=1-3}}}
{{{-2x=-2}}}
{{{x=1}}}
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Multiply eq. 4 by 2 and subtract from eq. 1,
{{{x+2y+2z-2y-2z=1-0}}}
{{{x=1}}}
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So,
{{{x=1}}}
and then from eq. 4,
{{{y=-z}}}