4D: Write an Equation

What does the "b" stand for in y=mx+b?

• slope

• x-intercept

• y-intercept

Answer explanation

If you substitube 0 for x, the value you're left with is "b" (y=b when x=0)

What letter represents the slope of a line in the equation y = mx + b?

• y

• m

• x

• b

Answer explanation

Rate of change: "m per x", always the number multiplied by the x variable

What is the equation for the line with a slope of 7 and passes through (0,1)?

• y = -7x + 1

• y = 7x + 1

• y = -1/7x - 1

• y = -1/7x + 1

Answer explanation

y=mx+b

slope(m): 7

y-intercept(0,b): (0,1)

y=7x+1

Given the equation y = 2x+3, what is the slope?

• 2

• x

• 3

Answer explanation

y=mx+b

slope(m)

y-intercept(0,b)

slope is 2, y-intercept is (0,3)

What is the y-intercept in the equation

y= -2x + 5

• (0,-2)

• (0,3)

• (0,5)

Answer explanation

y=mx+b

slope(m)

y-intercept(0,b)

slope is -2, y-intercept is (0,5)

Which graph shows a line for the following equation?:

 $y=\frac{2}{3}x-3$  

• a

• b

• c

• d

Answer explanation

Only graph with y-intercept of (0,-3) and a positive slope

Slope: 2/3 (rise 2, run 3)

Write an equation for the graph

• y=1/2x - 2

• y = 2x - 2

• y = 1/2x + 2

• y = 2x + 2

Answer explanation

Line through (4,0) & (0,-2)

y-intercept (0,b): (0,-2)

Slope (m):

$\frac{\Delta y}{\Delta x}=\frac{0-\left(-2\right)}{4-0}\ =\frac{0+2}{4}=\frac{2}{4}=\frac{1}{2}$
y=mx+b
$y=\frac{1}{2}x-2$

What is the equation of this line?

• 0

• undefined

• y = -2

• x = -2

Answer explanation

x=-2, no matter what the y-value is

slope is undefined (vertical line) & no y-intercept: cannot be written in slope intercept form

What is the equation of the line?

• y = -3/4x + 3

• y = 4/5x + 3

• y = -4/5x + 3

• y = -4/5x

Answer explanation

$y=-\frac{4}{5}x+3$

y=mx+b
slope(m): down 4, run 5 -4/5
y-intercept (0,b): (0,3)

What is the equation of the line in the graph?

• y = 3

• x = 3

• x = 0

Answer explanation

Horizontal line: slope (m) is 0 "this is zero fun"

y-intercept (0,b): (0,3)

y=mx+b

y=0x+b

y=b

y=3

*y is always 3, no matter what the value of x is