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 .
3x+5y=−1
3(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=1310=1.3 -
Now that we know the value of
y , substitute it back into the first equation and solve forx .
x=4−5y
x=4−5(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