Question 433602
x + 4y = 3
x = 4 - 4y 


4 - 4y + 4y = 3 {substituted 4 - 4y, in for x, into top equation}
4 = 3 {combined like terms}
= no solution


Note:
- when solving a system of equations, and the variable disappears, leaving
a false statement, there is "no solution", meaning these two lines never meet.
They are parallel lines.
- When solving a system of equations, and the variable disappears, leaving a 
statement that is always true, there are "infinite solutions", meaning the two lines are the same.
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