What is the solution to the system of equations: $6=-4x+y, -5x-y=21$ ?

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Answer 1 · 2016-11-23T07:20:55

$x=-3$ and $y=-6$

From the first equation we can determine a value for $y$ .

$6=-4x+y$

Add $4x$ to both sides.

$4x+6=y$

In the second equation, substitute $y$ with $color(red)((4x+6))$ .

$-5x-color(red)((4x+6))=21$

Open the brackets and simplify. The multiplication of a negative and a positive results in a negative.

$-5x-color(red)(4x-6)=21$

$-9x-6=21$

Add $6$ to both sides.

$-9x=27$

Divide both sides by $9$ .

$-x=3$ or $x=-3$

In the first equation, substitute $x$ with $-3$ .

$6=-4(-3)+y$

Open the brackets. The multiplication of two negatives results in a positive.

$6=12+y$

Subtract $12$ from both sides.

$-6=y$ or $y=-6$

What is the solution to the system of equations: 6=-4x+y, -5x-y=216=-4x+y, -5x-y=21?