Y-Intercept and Writing Equations using y=mx + b

Y-Intercept and Writing Equations using y=mx + b

Multiple Choice

The horizontal axis on a coordinate grid is the...

• y-axis

• x-axis

Multiple Choice

The vertical axis on a coordinate grid is the...

• y-axis

• x-axis

What is a y-intercept?

• A y-intercept is where a line crosses the y-axis.

• We use the letter b to represent the y-intercept.

Multiple Choice

What is the y-intercept of this graph?

• b = 4

• b = -1.5

Multiple Choice

What is the y-intercept of this graph?

• b = 1.6

• b = 1

Fill in the Blank

What is the y-intercept of this graph? Type your answer in the format b=? with no spaces.

Fill in the Blank

What is the y-intercept of this graph? Type your answer in the format b=? with no spaces.

Poll

What about this graph? What's the y-intercept?

• b = 0

• b = -3

• There is no y-intercept.

• The y-intercept is infinity.

What do we do with slope and the y-intercept?

Combining yesterday and today.

Writing Equations from Lines

• We can write an equation for any graphed line using its slope (m) and y-intercept (b).

• We find the slope using m=rise/run (pay attention to positive vs. negative slope)

• We find the y-intercept, b, by looking at the graph.

Multiple Choice

Which equation is for a line that has a slope (m) = -2 and a y-intercept (b) = 3?

• y = 3x - 2

• 3 = -2m + x

• y = -2x + 3

• -2 = mx + 3

Multiple Choice

Which equation is for a line that has a slope (m) = 4 and a y-intercept (b) = -1?

• y = 4x - 1

• 4= x + 1

• y = -x + 4

• m = 4x - b

Multiple Choice

Which equation is for a line that has a slope (m) = 5/2 and a y-intercept (b) = 1/2?

• y = 1/2x + 5/2

• y = 5/2x + 1/2

Multiple Choice

Which equation is for a line that has a slope (m) = 4 and a y-intercept (b) = -1?

• y = 4x - 1

• 4= x + 1

• y = -x + 4

• m = 4x - b

Fill in the Blank

Write the equation for a line with a slope of 7 and a y-intercept of 18. Use the format y=mx+b with no spaces.

Fill in the Blank

Write the equation for a line with a slope of -3 and a y-intercept of 0. Use the format y=mx+b with no spaces.

Fill in the Blank

Write the equation for a line with a slope of 1/2 and a y-intercept of -9. Use the format y=mx+b with no spaces.

Open Ended

Explain two things: What is the y-intercept? and How can we write equations for lines if we know the slope and the y-intercept?

Poll

How are you feeling about what we learned today?

• Great! I totally get it.

• Good. I get it for the most part.

• Meh. I feel like I'm missing something.

• Bad. I don't understand it at ALL.