Mickey and Minnie were tasked with graphing the equation `4x-3y=21.`

Question

Mickey and Minnie were tasked with graphing the equation `4x-3y=21.`

Mickey says that he will find the `x` and `y-intercepts,` then graph.

Minnie says she will transform the equation into `Slope\ Intercept\ Form`, then graph.

Who do you think is correct? Explain your reasoning!

(it is NOT enough to just say who you think is correct. Include why you think they are correct, and why the other one would be incorrect. Use math vocabulary that you learned in this lesson)

Answer 1

Hmm! You should notice something when you work out Mickey's technique and Minnie's technique. Let's dive a little into them:

Mickey's Approach:

To find the x-intercept of an equation, we set y=0 and solve for x in the equation:

4x -3(0) = 21

4x = 21

x = 21/4 or 5.25

:. x-intercept is (5.25,0)

To find the y-intercept of an equation, we set x=0 and solve for y in the equation:

4(0)-3y = 21

-3y = 21

y = -7

:. y-intercept is (0,-7)

Now all Mickey does plot those two points and draw a line through them. Let's see Minnie's approach:

She is going to convert the current equation into y = mx + b, where m is the slope and b is the y-intercept. Here's how she does it:

4x-3y = 21

-3y = -4x + 21

y = (-4/3)x - 7 (Whoa, the y-intercept is the same as Mickey's!)

If Minnie was to plot this graph, and compared it to Mickey's...they would see it's the same graph.

Hope this helps!