How do solve the following linear system?: $4x+21y=6 , x+y=-1$ ?

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Answer 1 · 2016-05-12T02:53:37

$x=-27/17$
$y=10/17$

Given -

$4x+21y=6$ ------------------ (1)
$x+y=-1$ --------------------(2)

Solve the equation (2) for $y$

$y=-1-x$

Substitute $y=-1-x$ in equation (1)

$4x+21(-1-x)=6$

Simplify

$4x-21-21x=6$
$-17x=6+21$
$x=-27/17$

Substitute $x=-27/17$ in equation (1)

$-27/17+y=-1$
$y=-1+27/17=(-17+27)/17=10/17$
$y=10/17$

How do solve the following linear system?: 4x+21y=6 , x+y=-1 4x+21y=6 , x+y=-1 ?