Question 370032
Substitution or elimination?
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Substitution:
1.{{{3x-4y=20}}}
2.{{{x+2y=5}}}
From eq. 2,
{{{x=5-2y}}}
Substitute into eq. 1,
{{{3(5-2y)-4y=20}}}
{{{15-6y-4y=20}}}
{{{-10y=5}}}
{{{highlight(y=-1/2)}}}
Then from eq. 2,
{{{x=5-2(-1/2)}}}
{{{x=5+1}}}
{{{highlight(x=6)}}}
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Elimination:
1.{{{3x-4y=20}}}
2.{{{x+2y=5}}}
Multiply eq. 2 by (2) and add to eq. 1,
{{{3x-4y+2x+4y=20+10}}}
{{{5x=30}}}
{{{highlight_green(x=6)}}}
Then use either equation to solve for {{{y}}}.
{{{18-4y=20}}}
{{{-4y=2}}}
{{{highlight_green(y=-1/2)}}}