How do I do algebra subsitution?

How do I do algebra substitution?
Thanks

1 Answer
Steve J.
Jul 9, 2018

See below.

Explanation:

Suppose you are told that #x + y = 6# and that #x = 2#. How do you figure out a value for y?

Substitute the value for x that you know (because of the 2nd equation you were given) for the x in the first equation.

#" "" "2#
#" "" "color(red)darr#
#" "" "x + y = 6 color(red)" yields " 2 + y = 6#

That completes the substitution. But you do not have a value for y yet. That requires another of algebra's tricks: do something that helps to both sides.

We now have #2 + y = 6#. Subtract 2 from both sides.

#2 + y - 2 = 6 - 2#

#" "" "y = 4#

I hope this helps,
Steve

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