Question

I DON’T KNOW WHAT I’M DOING WRONG
Solve the following systems using the elimination method.
5x-y=4
4x+y=5

1. diemthu
The end result of this exercise is x = 1, y = 1.
Step-by-step explanation:
To solve by elimination, the coefficients of one of the variables must coincide in the two equations, so that the variable vanishes when one equation is subtracted from the other.
• 5x−y=4,4x+y=5
To make 5x and 4x equal, multiply all the terms on each side of the first equation by 4 and all the terms on each side of the second by 5.
• 4×5x+4(−1)y=4×4, 5×4x+5y=5×5
Simplify.
• 20x−4y=16, 20x+5y=25
Subtract 20x+5y=25 from 20x−4y=16. To do this, subtract like terms on both sides of the equals sign.
• 20x−20x−4y−5y=16−25
Add 20x and −20x. Terms 20x and −20x cancel, leaving a single-variable equation that can be solved.
• −4y−5y=16−25
• −9y=16−25
• −9y=−9
Divide both sides by −9.
• y = 1 =====> First result
Substitute 1 for y in 4x+y=5. Since the resulting equation only contains one variable, it can be solved for x directly.
• 4x+1=5
Subtract 1 from both sides of the equation.
• 4x=4
Divide both sides by 4.
• x = 1 =====> Second result.