How do you find b?

How do you find b ?

How do you find

b

?

“DRY”

How do you find b (dry)?

Review What is slope-intercept form?

Y = mX + b ?

Review What is slope-intercept form?

Y = mX + b Input

Review What is slope-intercept form?

Y = mX + b ?

Review What is slope-intercept form?

Y = mX + b Output

Review What is slope-intercept form?

Y = mX + b ?

Review What is slope-intercept form?

Y = mX + b Rate of change a.k.a. Slope

Review What is slope-intercept form?

Y = mX + b ?

Review

How do you find b ?

What is slope-intercept form?

Y = mX + b Starting amount a.k.a. ‘y-intercept’

Riddle

b

I started with some money.

m

Every week I earned $100.

After 4 weeks, I had $900.

How much did I start with?

X Y

Riddle

b

I started with some money.

m

Every week I earned $100.

After 4 weeks, I had $900.

How much did I start with?

X Y 4 900

Riddle

b

I started with some money.

m

Every week I earned $100.

After 4 weeks, I had $900.

How much did I start with?

X 0 1 2 3 4 Y 900

Riddle

b

I started with some money.

m

Every week I earned $100.

After 4 weeks, I had $900.

How much did I start with?

X 0 1 2 3 4 Y 800 900

Riddle

b

I started with some money.

m

Every week I earned $100.

After 4 weeks, I had $900.

How much did I start with?

X 0 1 2 3 4 Y 700 800 900

Riddle

b

I started with some money.

m

Every week I earned $100.

After 4 weeks, I had $900.

How much did I start with?

X 0 1 2 3 4 Y 600 700 800 900

Riddle

b

I started with some money.

m

Every week I earned $100.

After 4 weeks, I had $900.

How much did I start with?

4 * 100

Gained $400

900 – 400

Started with $500 $500 X 0 1 2 3 4 Y 500 600 700 800 900

“DRY”

Write the equation of the linear relationship with:

m

m: 100 Y = mX + b

x y

point: (4, 900).

900 = 100(4) + b 900 = 400 + b – 400 –400 500 = b Y = 100X + 500

Ex. 1: Write the equation of a line that goes through (7, 8) and has a slope of 2. Y = mX + b Y = 2X – 6 NEED m and b NEED b!!!

How to use (7, 8)???

Input

X

Output

Y

Ex. 1: Write the equation of a line that goes through (7, 8) and has a slope of 2. Y = mX + b Y = 2X – 6 8 = 2 ( 7 ) + b 8 = 14 + b – 14 – 14 -6 = b How to use (7, 8)???

Input

X

Output

Y

Ex. 2: Write the equation of a line with this information: m slope: -5 X Y point: (-4, 3) Y = mX + b 3 is NOT y-intercept!!!

Ex. 2: Write the equation of a line with this information: m slope: -5 X Y point: (-4, 3) Y = -5X – 17 Y = mX + b 3 = -5 ( -4 ) + b 3 = 20 + b – 20 – 20 -17 = b

NEED m Ex. 3: Write the equation of a line that goes through (0, 8) and has a slope of 2. and b Y = mX + b Y = 2X + 8

NEED m Ex. 3: Write the equation of a line that goes through (0, 8) and has a slope of 2. and b Y = mX + b Y = 2X + 8

Ex. 4: Write a rule from this information: m X Y m: -4 point: (8, -2) Y = mX + b -2 = -4 ( 8 ) + b -2 = -32 + b + 32 + 32 30 = b Y = -4X + 30

Ex. 5: Write an equation for a relationship with this information: m: zero . point: (-4, -6) The change in y when x increases by one Y = -6

Ex. 6: Write an equation for a relationship with this information: m: undefined . point: (-4, -6) The change in y when x increases by one X = -4

The End