How do you solve the system?: $X + Y = - 1, Y = 3 X - 17$ $X+Y= -1, Y=3X-17$

Question

1501 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2018-03-02T06:47:04

$X = 4, Y = - 5$ $X=4, Y=-5$

If we know $Y = 3 X - 17,$ $Y=3X-17,$ we can just go ahead and replace $Y$ $Y$ in $X + Y = - 1$ $X+Y=-1$ with $3 X - 17$ $3X-17$

$X + Y = - 1 \Leftrightarrow X + 3 X - 17 = - 1$ $X+Y=-1hArrX+3X-17=-1$

Now, we have an equation with one unknown variable, which can be easily solved.

$4 X - 17 = - 1$ $4X-17=-1$

$4 X = - 1 + 17 = 16$ $4X=-1+17=16$

$X = \frac{16}{4} = 4$ $X=16/4=4$

We need $Y .$ $Y.$ We know $X = 4,$ $X=4,$ so we can plug in $4$ $4$ for $X$ $X$ in $X + Y = - 1$ $X+Y=-1$ and solve for $Y :$ $Y:$

$4 + Y = - 1$ $4+Y=-1$

$Y = - 1 - 4 = - 5$ $Y=-1-4=-5$

How do you solve the system?: X+Y=−1,Y=3X−17X+Y= -1, Y=3X-17