Equations are something that you will constantly be using throughout your math career. Learning and understanding the basics is an integral part of "getting off on the right foot" when dealing with math. This section will help you better understand, work with, and solve equations when they have addition and/or subtraction in them.
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Changing the order of the addends (numbers you're adding) doesn't change their sum (what they equal when added together). Example: a + (b + c) = (a + b) + c
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Any number plus 0 (zero) equals itself. Example: a + 0
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= a
If two sides of an equation are equal, you can add or subtract the same amount to both sides, and they will still be equal. Example: a = b a + c = b + c a - c = b - c
When solving equations, remember that addition and subtraction are inverse operations - they undo each other (i.e., 10 + 9 - 9 = 10). To solve equations using addition and subtraction, first decide which operation has been applied, then use the inverse operation to undo this (remember to add or subtract from both sides of the equation).
1.
Solve:
x + 79 = 194
Solution: x + 79 = 194 x + 79 - 79 = 194 - 79 x = 115
2.
Solve:
You need to get the variable by itself (isolate the variable). To undo adding 79, subtract 79 from both sides.
x - 56 = 604
Solution:
x - 56 = 604 x - 56 + 56 = 604 + 56 x = 660
You need to isolate the variable. To undo subtracting 56, add 56 to both sides.
This section will help you understand, work with, and solve equations of a slightly more complex nature - equations involving the use of multiplication and/or division.
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Order of operations: The operations inside parentheses () and brackets [] are done first. Then any operations involving exponents (which you will learn about later). Then do all multiplying and dividing from left to right. Finally, do all addition and subtraction from left to right.
Multiplication can be written three different ways: 9*x 9x 9(x)
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A fraction bar is also a division symbol.
Changing the order of multipliers (numbers you're multiplying together) doesn't change their product (total when the numbers are multiplied together). Example: ab = ba
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Zero times any number is zero and 1 times any number is the number. Examples: x(0) = 0 (0)x = 0 x(1)= x 1*x=x
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If two sides of an equation are equal, you can multiply or divide each side by the same quantity (number or equation)
and it will still be equal. Examples: a = b, c <> 0 ac = bc (a / c) = (b / c)
When solving equations, remember that multiplication and division are inverse operations, therefore they undo each other (i.e., (4 * 8)/8 = 4). To solve equations using multiplication or division, first decide which operation has been applied, then use the inverse operation to undo this (remember to multiply or divide on both sides o f the equation).
1.
Solve:
6x = 36
Solution: 6x = 36 (6x) / 6 = 36 / 6
You need to get the variable by itself (isolate the variable). To undo multiplying by 6, divide by 6 on both sides.
x = 6
2. 10
Solve:
x / 5 =
Solution: x / 5 = 10 5(x / 5) = 10(5) x = 50
You need to isolate the variable. To undo dividing by 5, multiply both sides by 5
This section will help you understand, work with, and solve complex equations that involve different combinations of multiplication, division, addition, and subtraction.
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Order of operations: The operations inside parentheses () and brackets [] are done first. Then any operations involving exponents (which you will learn about later). Then do all multiplying and dividing from left to right. Finally, do all addition and subtraction from left to right.
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Multiplication can be written three different ways:
7*x 7x 7(x)
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A fraction bar is also a division symbol.
Also, be sure to refer to the above sections if you have forgotten or need to review any of the other material covered.
When solving complex equations, like the ones used in the examples below, be sure to remember that multiplication and division are inverse operations along with addition and subtraction. Therefore, they undo each other (i.e., (5 * 2)/2 = 5 or 10 + 4 - 4 = 10). To solve these equations, first decide which operation has been applied and then use the inverse operation to undo this (remember to apply the operation to both sides of the equation).
1. 42
Solve:
7x - 7 =
Solution: 7x - 7 = 42 7x - 7 + 7 = 42 +
7 7x = 49 (7x) / 7 = 49 / 7 x = 7
2. Solve: = 25
The variable needs to be isolated. To undo subtracting 7, add 7 to both sides. Adding 7 hasn't isolated the variable, so we need to continue. To undo multiplying by 7, divide both sides by 7.
5(x + 2)
Solution: 5(x + 2) = 25 [5(x + 2]/5 = 25/5 x + 2 = 5 x + 2 -2 = 5 -2 x = 3
The variable needs to be isolated. To undo multiplying by 5, divide by 5 on both sides. Dividing by 5 hasn't isolated the variable, so we need to continue. To undo adding 2, subtract 2, from both sides.
