# The Weekend!!!

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"The Weekend!!!"

```					             The Weekend!!!
• Today is Friday January 11, 2008.

• Last Day to turn in your Student Information
Sheet!!!

calculator, (3rd & 5th) take out your practice
problems and your word problem worksheet.

• We will begin with a bell-ringer as soon as the
bell rings.
Mod 3 Bell-ringer
1. Describe how to write an equation given a slope
and one point?

2. What is the y-coordinate for the x-intercept?
Summary
•    Given the slope & y-intercept.
1.   Find the slope.
2.   Find the y-intercept.
3.   What variables represent each?
4.   Substitute values (m, b) into
equation y = mx+b.
Summary
•    Given the slope and a point:
1. Find the slope.
2. Substitute x, y from given point into
equation y = mx + b.
3. Solve to locate y – intercept.
4. Substitute values (m, b) into
equation y = mx + b.
• David Margolez has been working for
Pioneer Engineering since 1990. Each
year he gets a \$2,100 raise. In 1998, he
earned \$33,600.
– What information do we know?
• M=    2,100
• B=
• X=     8
• Y=    33,600
– Substitute information into y = mx + b
• Between 2000 and 2006, the monthly rent
for a one-bedroom apartment increased by
\$35 per year. In 2004 the rent was \$420
per month.
• You work at a travel agency and you are
given a \$1,500 raise at the end of each
year. After working 3 years your salary is
\$21,000.
We know how to write an equation when
given a slope and y-intercept.
We know how to write an equation when
given a slope and a point.
What do we do when we aren’t given a
slope?
What if we’re given two points?
We still have to find a slope?
What do you suggest?
Writing an Equation when
given two points.
(1, 6) (3, 7)
• Find slope using slope   • What two pieces of
formula.                   information do I need?
6–7                        – M?   ½
1–3                        – B?   5½
• My slope is ½            • Now choose one of the
• 6 = ½ (1) + b              given points.
6=½+b                    • Using the x and y from
5½=b                       chosen point replace into
• Y=½x+5½                    equation y = mx + b
• Write the equation for
y = mx + b
Summary
•    Given two points:
y 2  y1
1. Use the formula   m              to find slope.
x 2  x1
2. Chose either of the given points.
3. Substitute x, y from chosen point into
equation y = mx + b.
4. Solve to locate y – intercept.
5. Substitute values (m, b) into
equation y = mx + b.
• Complete problems 8-10 on Practice
Worksheet
Write the equation of the line below.
a) Find the slope of
the line.
• M = -3/5

b) Find the y-
intercept.
• Take one of the
points on the
line, either (-2, 5)
or (3, 2) and
substitute into
y = mx + b.
• B = 19/5
c) Y = -3/5 x + 19/5
Summary
•    Given a graph:
1. Identify 2 points on the line.
2. Use the formula m  2
y  y1    to find slope.
x 2  x1
3. Chose either of the given points
4. Substitute x, y from chosen point into
equation y = mx + b.
5. Solve to locate y – intercept.
6. Substitute values (m, b) into
equation y = mx + b.
What type of lines are
these?
Parallel Lines

a) Find the slope of
the purple line.
b) Find the slope of
the red line.
c) What do you
notice?
d) Do the lines have
the same y-
intercept?
Conclusion:
Parallel lines have the
same slope, but
different y-
intercepts.
• Write the equation of a line parallel to
the line y = x + 4 that passes through
the point (-2, 0).
– What is the slope of the original line?
– What is the slope of the new line?
– Is the new line going to have the same y-
intercept?
– Find the y-intercept of the new line using
the slope and the given point.
• Write the equation of a line parallel to
the line y = -3x + 1 and passes through
the point (4, 2).

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