Scribe Post

Today in class we decided to move the test to tomorrow and went over problems that were hard for us on the last couple homework assignments. Since we get an extra night to study my post is going to be going over important things to know for the test. I am going to go over some problems and terms that are important to know from section 2.1-2.3. I am not going to go over everything from these sections because some things have been explained in other scribe posts. I am just going to go over things I have found confusing from these sections. Also remember that you can bring in a page of math tweets to use during your test tomorrow. They have to be printed from the favorite page or a screen shot of the favorite page then printed. If you dont do this you can't use them during the test.

Section 2.1
Recognizing Conditional Equations, Identities, and Contradictions
1.Conditional
One solution
Final line is x=a number
2. Contradiction
None; solution set is 0 with a / threw it
Final line is false, such as -15=120
3. Identity
Infinite; solution set, all real numbers
Final line is true, such as 0=0

Section 2.2
Solving for a Specified Variable
Example: Solve for t.
prt=I
(pr)t=I associative property
(pr)t/pr=I/pr divide by pr.
t=I/pr
Steps for solving for a Specified Variable
Step 1: Transform so that all terms contain the specified variable are on one side of the equation and all terms without that variable are on the other side.
Step 2: If necessary, use the distributive property to combine the terms with the specified variable. The result should be the product of a sum or the difference and the variable.
Step 3: Divide each side y the factor that is the coefficient of the specified variable.
Section 2.3
It's important to remember how to translate words to mathmatical expressions.
*This was explained on Christines scribe post earlier this week.
Remember the Difference Between Expression and Equation
Expression:
Example: x=5
Equation:
Example: x+2=4
Solving an Investment Problem
Example:
After winning the state lottery, Mark LeBeau has $40,00 to invest. He will put part of the money in an account paying 4% interest and the remainder into stocks paying 6% interest. His accountant tells him that the total annual income from these investments should be $2,040. How much should he invest at each rate?
Step 1: Reas the problem again. We must find the two amounts.
Step 2: Assign a variable
Let x= the amount to invest at 4%
Let 40,000-x= the amount to invest at 6%
The formula for interest is I=prt. Here the time, t, is one year. Make a table to organize the given information.
You can look up the table for this equation on page 82 in your math book.
Step 3: Write an equation. We do so without clearing decimals.
.04+.06(40,000-x)=2040
Step 4: Solve the equation. We do so without clearing decimals.
.04+.06(40,000)-.06x=204o Distributive Property
.04x+2,400-.06x=20 Multiply
-.02x+2,400=2,040 Combine Like Terms
-.02x=-360 Subtract 2,400
x=18,00 Divide by -.02
Step 5: State the answer. Mark should invest $18,000 at 4%. At 6%, he should invest $40,000-$18,000=$22,000.
Step 6: Check bby finding the annual interest at each rate; they should total $2,040.
.04($18,000)=$720 and .06($22,000)=$1,320
$720+$1,320=$2,040, as required.
The Next Scribe Post will be done by Emma