How do you solve x + y = 1 and 3x – y = 11?

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Answer 1 · 2018-04-11T21:53:08

$y = - 2$ $y=-2$ and $x = 3$ $x=3$ .

You need to use simultaneous equations. Make $x$ $x$ or $y$ $y$ the subject from one equation and substitute it into the other.

$x = 1 - y$ $x=1-y$

Then

$3 (1 - y) - y = 11$ $3(1-y)-y=11$

$3 - 3 y - y = 11$ $3-3y-y=11$

$3 - 4 y = 11$ $3-4y=11$

$4 y = - 8$ $4y=-8$

$y = - 2$ $y=-2$

If $y = - 2$ $y=-2$ , substitute back into either equation to find $x$ $x$ .

$x - 2 = 1$ $x-2=1$

$x = 3$ $x=3$