Question

2x + y = 3

x - 2y = -1

If equation two is multiplied by -2 and then the equations are added, the result is _____.

A.) -3y = 3

B.) 3y = 5

C.) 5y = 5

Answer 1

It's C.) 5y = 5 not B

They want you to multiply -2 by the bottom equation which is

x - 2y = -1

So you will be taking each individual number in this equation and multiplying it by -2

Remember when multiplying a negative number by another negative number it will create a positive one

x - 2y = -1

The underlined numbers in the equation correlate with the numbers I am multiplying by -2

x * -2 = -2x

-2y * -2 = 4y

-1 * -2 = 2

So the new equation would be -2x + 4y = 2

now add

2x + y = 3

and

-2x + 4y = 2

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1st equation 2x + y = 3

2nd equation -2x + 4y = 2

1 2 3

(2x + -2x) + (y + 4y) = (3 + 2)

1. 2x and -2x cancel each other out and you get 0

2. y + 4y is just 1y + 4y which is 5y

3. and 3 + 2 is 5

which leaves us with

5y = 5

Answer 2

It should be B 3y=5 hope I'm right.