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Door 3 ยท Grade 7

๐Ÿงฉ Exponents & Powers

Exponent = how many times the base is multiplied by itself

โ–ถ Play Door 3

Writing Repeated Multiplication as Exponents

An exponent tells how many times to multiply a number (the base) by itself.
5 x 5 x 5 = 5ยณ (read as '5 to the power of 3' or '5 cubed')
TermMeaningExampleBaseThe number being multiplied5ExponentHow many times to multiply3PowerThe whole expression5ยณ = 125Special cases:
โ€ข a^1 = a (any number to power 1 is itself)
โ€ข a^0 = 1 (any nonzero number to power 0 is 1)
โ€ข 1^n = 1 (one raised to any power is 1)

Worked example

Problem: Write 7 x 7 x 7 x 7 using exponents.

  1. 7^4 (four 7's multiplied together)

Answer: 7^4 (four 7's multiplied together)

Negative Bases & Order of Operations

Negative bases with exponents: Parentheses make a critical difference!
ExpressionMeaningResult(-2)^4(-2) x (-2) x (-2) x (-2)+16 (positive)-2^4-(2 x 2 x 2 x 2)-16 (negative)Key rule: Even exponent on a negative base gives a positive result. Odd exponent on a negative base gives a negative result.
Order of Operations (PEMDAS):
โ€ข Parentheses
โ€ข Exponents
โ€ข Multiplication and Division (left to right)
โ€ข Addition and Subtraction (left to right)

Worked example

Problem: Evaluate: (-3)ยณ vs -3ยณ

  1. (-3)ยณ = (-3) x (-3) x (-3) = -27.
  2. Also -3ยณ = -(3x3x3) = -27.
  3. Same result because exponent is odd.

Answer: Same result because exponent is odd.