Econ303 Math Review: Solving Equations and Applying the Rule of Power and Logs - Prof. Rui, Study notes of Macroeconomics

Examples and rules for solving linear equations with one unknown variable, applying the rule of power, and solving equations with two unknown variables. Students enrolled in economics 303 or similar courses will find this review helpful for understanding mathematical concepts essential for their studies.

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Pre 2010

Uploaded on 03/10/2009

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Econ303 Math Review 1
1 Solving for one unknown variable x
1.1 linear
Example 1: 3x= 5
x= 5/3 = 1.67
Example 2: 1.5+3x= 6 + 1.5x
3x1.5x= 6 1.5
1.5x= 4.5
x= 3
Example 3: 3x= 1 2x
3x+ 2x= 1
5x= 1
x= 1/5 = 0.2
Example 4: 12(x5) = 3(x+ 10)
12x60 = 3x+ 30
12x3x= 30 + 60
9x= 90
x= 90/9 = 10
Example 5: 5
x= 6
5 = 6x
x= 5/6
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1 Solving for one unknown variable x

1.1 linear

Example 1: 3x = 5 x = 5/3 = 1. 67 Example 2: 1.5 + 3x = 6 + 1. 5 x

3 x − 1. 5 x = 6 − 1. 5

  1. 5 x = 4. 5 x = 3 Example 3: 3x = 1 − 2 x

3 x + 2x = 1 5 x = 1 x = 1/5 = 0. 2 Example 4: 12(x − 5) = 3(x + 10) 12 x − 60 = 3x + 30 12 x − 3 x = 30 + 60 9 x = 90 x = 90/9 = 10 Example 5: (^5) x = 6

5 = 6x x = 5/ 6

1.2 rule of power

Let a and b any real number. xa^ · xb^ = xa+b xa xb^ =^ x

a−b x−a^ = (^) x^1 a (xa)b^ = xa·b (xa)^1 /a^ = xa·^1 /a^ = x Example 1: x^0.^5 = 7

x = 7^1 /^0.^5 = 49 Example 2: 7x^0.^3 = 5x (^7)

5 =^

x x^0.^3 1 .4 = x^1 −^0.^3 x^0.^7 = 1. 4 x = 1. 41 /^0.^7 Example 3: (^) x^50. 3 = 2x^2 5 2 =^ x (^2) · x 0. 3 x^2.^3 = 2. 5 x = 2. 51 /^2.^3 Example 4: √ 3 − 5 x = 2 3 − 5 x = 2^2 = 4 5 x = 3 − 4 = − 1 x = − 1 / 5 Example 5: √x = 2√ 5 − x

x = 4(5 − x) x = 20 − 4 x x + 4x = 5x = 20 x = 20/5 = 4