Answer:
C, D, E and F
Step-by-step explanation:
Given
4x+5y=18
6x−5y=20
Required
Determine which procedure will result in a single equation in one variable
To do this; we'll test each of the options
A. Subtract the first equation from the second equation.
[tex](6x - 5y=20) - (4x+5y=18)[/tex]
[tex]6x - 4x - 5y - 5y = 20 - 18[/tex]
[tex]2x - 10y = 2[/tex] --- This didn't produce the desired result
B. Subtract the second equation from the first equation.
[tex](4x+5y=18) - (6x - 5y=20)[/tex]
[tex]4x - 6x + 5y + 5y =18 - 20[/tex]
[tex]-2x + 10y = -2[/tex] --- This didn't produce the desired result
C. Multiply the first equation by 18; multiply the second equation by 18; add the equations.
First Equation
[tex]18 * (4x+5y=18)[/tex]
[tex]72x + 90y = 324[/tex]
Second Equation
[tex]18 * (6x - 5y=20)[/tex]
[tex]108x - 90y = 360[/tex]
Add Resulting Equations
[tex](72x + 90y = 324) + (108x - 90y = 360)[/tex]
[tex]72x + 108x + 90y - 90y = 324 + 360[/tex]
[tex]72x + 108x = 324 + 360[/tex]
[tex]180x = 684[/tex] --- This procedure is valid
D. Multiply the first equation by − 6; multiply the second equation by 4; add the two equations.
First Equation
[tex]-6 * (4x+5y=18)[/tex]
[tex]-24x - 30y = -108[/tex]
Second Equation
[tex]4 * (6x - 5y=20)[/tex]
[tex]24x - 20y = 80[/tex]
Add Resulting Equations
[tex](-24x - 30y = -108) + (24x - 20y = 80)[/tex]
[tex]-24x + 24x - 30y -20y = -108+ 80[/tex]
[tex]-50y = -28[/tex]
[tex]50y = 28[/tex] --- This procedure is valid
E. Multiply the first equation by 3; multiply the second equation by − 2; add the two equations.
First Equation
[tex]3 * (4x+5y=18)[/tex]
[tex]12x + 15y = 54[/tex]
Second Equation
[tex]-2 * (6x - 5y=20)[/tex]
[tex]-12x + 10y = -40[/tex]
Add Resulting Equations
[tex](12x + 15y = 54) + (-12x + 10y = -40)[/tex]
[tex]12x - 12x + 15y - 10y =54 - 40[/tex]
[tex]5y = 14[/tex] --- This procedure is valid
F. Multiply the first equation by 3; multiply the second equation by 2; subtract the equations in any order
First Equation
[tex]3 * (4x+5y=18)[/tex]
[tex]12x + 15y = 54[/tex]
Second Equation
[tex]2 * (6x - 5y=20)[/tex]
[tex]12x - 10y = 40[/tex]
Subtract equation 1 from 2 or 2 from 1 will eliminate x;
Hence, the procedure is also valid;
