The pair of equations:
y = x + 4
y = -2x - 2
To solve the system of equation by substitution, you would substitute one variable for it's equivalent expression. Combining the pair of equations into one equation in only one variable. The easiest way to do this is by substituting out the variable y because it is already alone on one side of the equal sign. Substitute the y in the second equation for: x+4
x+4 = -2x - 2
solve for x
x + 2x = -2 -4
3x = -6
x = -2
now use the value for x to find y by putting into either equation.
y = x + 4
y = (-2) + 4
y = 2
solution is: (-2, 2)
The answer is 0
5+3(5)-10(2)
=5+15-20
=20-20
=0
