How do you solve x+5y=4 and 3x+15y=-1 using substitution?
x+5y=4
3x+15y=-1
x+5y=4
3x+15y=-1
2 Answers
Explanation:
SUBSTITUTION means substituting one of the variables for a different value in an equation, which can allow you to solve the equation.
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To get the value of one of the variables, isolate the variable in one of the equations (choose the simpler equation to make life easier).
x+5y=4
x=4-5y -
Substitute (hence the method name "substitution")
x in the other equation for the value ofx .
3color(blue)x+5y=-1
3color(blue)((4-5y))+5y=-1 -
Now that we have like variables in the equation, we can solve for
y .
3(4-5y)+5y=-1
12-15y+5y=-1
12-10y=-1
-10y=-13
y=13/10=1.3 -
Now that we know the value of
y , substitute it back into the first equation and solve forx .
x=4-5color(green)y
x=4-5color(green)((1.3))
x=4-6.5
x=-2.5
Answer (Coordinate Form):
y=-0.5
x=6.5
Explanation:
Get x by it's self in the first equation which is