Can someone please explain to me how to use the substitution method to solve this problem?

Question

anonymous · Answer

attachment

hero · Answer

y = 2x + 3
5x - y = -3


Using substitution:

5x - (2x + 3) = -3

Now solve

anonymous · Answer

We are looking for an ordered pair (point on a graph) that satisfies both eq. in the system.
Substution means just that.  Substituting a value for an unknown, "y" say.  If we were to substitiute "1" say for the value of "y" in the 2d eq. ( 5x-y=-3) and solve for "x" we would have 1/2 of the ordered pair (the "x" part).  The other 1/2 of the ordered pair would be the "1" that we subsituted at the beginning.

Now back to your problem.  Here you don't have a definite value for 
"y", you have and expression that is an equivalent value of Y.  But you can still use it.
Substitute 2x+3 in place of y in the 2d eq.

5x-y=-3
5x-1(2x+3)=-3
5x-2x-3=-3
3x-3=-3
3x-3+3=-3+3
3x=0
3/3x = 0/3
x=0                                 this is 1/2 of the ordered pair we are looking for.


Substitute 0 into the first eq.

y=2x+3
y=2(0)+3
y= 0 +3
y=3                         So the ordered pair we are looking for that satisfies the system
                                of  equations is              (0,3)