Archive for 02/16/2011


Rules to remember for monomials

  • When you multiply coefficients, you add exponents
  • When you divide coefficients, you subtract exponents
  • When you raise an exponent to a power, you multiply exponents

STEPS TO SOLVING SYSTEM OF EQUATIONS WORD PROBLEMS

1. Identify the variables

2. Write the system of equations

3. Solve

4. Check your answer

5. Write your answer in  a sentence to demonstrate your understanding of what you have found

example

Robert bought pizzas and sodas from Key Pizza. He purchased 2 bottles of soda for every box of pizza that he bought. The individual cost of pizza and soda is $5 and $1 dollar respectively. Robert spent a total of $56.00. How many boxes of pizzas and bottles of soda did Robert buy from Key Pizza?

step 1

x = number of pizzas, y = number of bottled sodas

step 2

2x = y

5x + y = 56

step 3

5x + 2x = 56 ——> 7x = 56 —–>  7x/7 = 56/7 —–> y = 8

2(8) = y —-> 16 = y

step 4

2(8) = 16 —-> 16 = 16—–> CHECK

5(8) + 16 = 56 —-> 40+ 16 = 56—–> 56 = 56——> CHECK

step 5

Robert bought 8 boxes of pizza and 16 bottles of soda from Key Pizza.

MONOMIALS WITH…

ONE VARIABLE

with a negative
without a negative

MORE THAN ONE VARIABLE

 

with negative exponent

without negative exponent

RAISE FRACTION TO A POWER

To simply: =

Without negative exponents:

COMBINING DIVISION AND RAISING TO NEGATIVE POWERS

THINGS TO REMEMBER…
  • Raise whole numbers to a power
  • Always solve what is in the parentheses first
  • Divide your coefficients
  • Multiply everything in the parentheses

x + 7y= -3      3x-2y= -9

1. Choose one of the three methods (graphing, elimination, substitution) to solve for x and y. For this example, it is best to choose the elimination method

Whether you choose to eliminate x or y, you will still receive the same end result.

-3(x+7y = -3) distribute negative two by all the numbers in the parentheses

1(3x – 2y = -9) distribute negative two by all the numbers in the parentheses

2. Rewrite the new equations so that the y values cancel out.

-3x-21y = 9 The x values are eliminated.

3x-2y = -9 Negative two y subtracted from negative twenty-one y equals negative twenty-three y.                                  Negative  nine subtracted from positive nine equals zero.

3. Solve for x by substituting your y-value into the second equation.

y=0

x + 7(0) = -3

x + 0 = -3

x = -3

Therefore, your solution is (3,0)

4. Check your answer by substituting your x and y values into the original equations.

3 + 7(0) = -3  ———> 3 +0 = -3 ———> 3 = 3                      CHECK

3(-3 ) – 2( 0 ) = -9 ———-> -9 – 0 = -9 ——–> -9 = -9         CHECK

 

Stacy went to the store last Wednesday to purchase 13 bags of chips and 7 cases of soda. The total of her groceries was $35.25. The cost of one bag of chips and one case of soda combined was $3.75. What is the price of one bag of chips and one case of soda?

STEP 1 Identify your variables.

x= bags of chips

y= cases of sodas

STEP 2 Write your two equations.

x + y = $3.75

13x + 7y = 35.25

STEP 3 Solve.

x + y = 3.75 ———> x-x +y = -x + 3.75 ———-> y = -x + 3.75

substitute y = -x + 3.75 into your second equation.

13x + 7(-x + 3.75) = 35.25 ——–> 13x -7x + 26.25 = 35.25 ——> -4x + 26.25 = 35.25 ——->

-4x + 26.25 – 26.25 = 35.25-26.25 ——> -4x = 9.00 —–> -4x/4 = 9.00/4 —–> x= 1.5

substitute 1.5 for x into your first equation.

1.5 + y = 3.75 —–> 1.5 – 1.5 + y = 3.75 ——> y = 3.75-1.5 —–> y = 2.25

STEP 4 Check your answer.

1st equation 1.5 + 2.25 = 3.75 —–> 3.75 = 3.75  CHECK

2nd equation 13(1.5) + 7(2.25) = 35.25 ——> 19.5 + 5.75 = 35.25 ——> 35.25 = 35.25 CHECK

STEP 5 Answer your question by writing a sentence.

The price of one bag of chips is $1.50. The price of 1 case of soda is $2.25.

 


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