Question

A teacher wrote the equation 3y + 12 = 6x on the board. For what value of b would the additional equation 2y = 4x + b form a system of linear equations with infinitely many solutions?

b = –8
b = –4
b = 2
b = 6

Answer 1

-8

Explanation:

Just took test lol

Answer 2

Answer: First option.

Explanation:

The equation of the line in Slope-Intercept form is:

`y=mx+b`

Where "m" is the slope of the line and "b" is the y-intercept

We need to write each equation in Slope-Intercept form:

First equation

`3y + 12 = 6x\\\\3y=6x-12\\\\y=2x-4`

Second equation

`2y = 4x + b \\\\y=2x+(b)/(2)`

Since, by definition, a system of linear equations has infinitely many solutions when the lines are the same, we can say that:

`y=y\\\\2x-4=2x+(b)/(2)`

Then, solving for "b", we get:

`-4=(b)/(2)\\\\(-4)(2)=b\\\\b=-8`