Science

Math

Humanities

... and beyond

Socratic Meta
Featured Answers

Topics

How do you solve $9x+7y = -65$ and $x= -1-7y$ using substitution?

1 Answer

Mar 26, 2016

Given
[1] $color(white)("XXX")9x+7y=-65$
[2] $color(white)("XXX")x=-1-7y$

By substitution
Substituting $(-1-7y)$ from [2] into [1] for $x$
[3] $color(white)("XXX")9(-1-7y)+7y=-65$
Simplifying
[4] $color(white)("XXX")-9-63y+7y=-65$

[5] $color(white)("XXX")-56y=-56$

[6] $color(white)("XXX")y=1$

Substituting $1$ from [6] into [2] for $y$
[7] $color(white)("XXX")x=-1-7(1)$
Simplifying
[8] $color(white)("XXX")x=-8$

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Verify by substituting $(x,y)=(-8,1)$ into equation [1]

Related questions

See all questions in Systems Using Substitution

Impact of this question

1528 views around the world

You can reuse this answer
Creative Commons License