Why did you multiply the first equation by -3

Answer 1

Clues:

"Algebra 1"

"first equation"

"multiply"

Since there is more than one equation, I will guess that multiplying the first equation by "-3" makes at least one of the coefficients in the first equation equal to (or opposite from) the corresponding coefficient in another equation. This means that this term may be ELIMINATED by either adding or subtracting the equations.

For example:

x + 2y = 10 [first equation]

3x + y = 25 [second equation]

Multiply the first equation by "-3" so we can add the equations and ELIMINATE the x terms:

-3x - 6y = -30

3x + y = 15

---------------------------- [ELIMINATION; add equations]

-5y = -15

y = 3 [with the x term ELIMINATED, you may solve for y]

Now, look at the original equations. We could have multiplied the second equation by "-2" to ELIMINATE the y term.

That's why this process is called the ELIMINATION METHOD.

-- Elementary, my dear Watson.