How do you solve x + y = 4 and y = 2x + 1?

1 Answer
Ben
Mar 24, 2018

Using substitution, you can find the solution is #x=1, y=3#

Explanation:

The second expression #y=2x+1# is already an expression ready to substitute! Since we know what #y# is equivalent to, we can substitute it into the first expression:

#x+y=4#

#x+(2x+1)=4 rArr x+2x+1=4#

#x(1+2)+1=4 rArr 3x+1=4#

#3xcancel(+1-1)=4-1 rArr 3x=3#

#color(red)(x=1)#

Now that we know what #x# is equivalent to, we can solve for #y#

#y=2x+1 rArr y=2(1)+1=2+1#

#color(blue)(y=3)#

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