Simplify b³ × 3b² × 2b⁻² : Complete Exponent Multiplication

Exponent Rules with Mixed Coefficients

Simplify the following problem:

b3×3b2×2b2= b^3\times3b^2\times2b^{-2}=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Simplify the following expression
00:03 Let's solve the product of the numbers
00:11 When multiplying powers with equal bases
00:16 The power of the result equals the sum of the powers
00:23 We'll apply this formula to our exercise and add the powers together
00:36 This is the solution

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Simplify the following problem:

b3×3b2×2b2= b^3\times3b^2\times2b^{-2}=

2

Step-by-step solution

Note that there is multiplication between all terms in the expression. Thus we'll first apply the distributive property of multiplication to understand that we can separately handle the coefficients of the terms raised to powers, and the terms themselves separately. For clarity, let's handle it in steps:

b33b22b2=32b3b2b2=6b3b2b2 b^3\cdot3b^2\cdot2b^{-2}=3\cdot2\cdot b^3\cdot b^2\cdot b^{-2}=6\cdot b^3\cdot b^2\cdot b^{-2}

Given that there is multiplication between all terms, we could do this. It should be noted that we can (and it's preferable to) skip the middle step, meaning:

Write directly:b33b22b2=6b3b2b2 b^3\cdot3b^2\cdot2b^{-2}=6\cdot b^3\cdot b^2\cdot b^{-2}

From here on we will no longer write the multiplication sign and remember that it is conventional to simply place the terms next to each other\ place the term next to its coefficient to indicate multiplication between them,

Proceed to apply the law of exponents for multiplication of terms with identical bases:

aman=am+n a^m\cdot a^n=a^{m+n}

Note that this law applies to any number of terms being multiplied and not just two, for example for three terms with identical bases we obtain the following:

amanak=am+nak=am+n+k a^m\cdot a^n\cdot a^k=a^{m+n}\cdot a^k=a^{m+n+k}

When we used the above law of exponents twice, we can also perform the same calculation for four terms in multiplication, five and so on..

Let's return to the problem and apply the above law of exponents:

6b3b2b2=6b3+22=6b3 6b^3b^2b^{-2}=6b^{3+2-2}=6b^3

Therefore, the correct answer is A.

Important note:

Here we need to emphasize that we should always ask the question - what does the exponent apply to?

For example, in this problem the exponent applies only to the b b bases and not to the numbers, more clearly, in the following expression: 5c7 5c^7 The exponent applies only to c c and not to the number 5,

whereas when we write: (5c)7 (5c)^7 The exponent applies to each of the terms in the multiplication within the parentheses,

meaning:(5c)7=57c7 (5c)^7=5^7c^7

This is actually the application of the law of exponents:

(xy)n=xnyn (x\cdot y)^n=x^n\cdot y^n

Which follows both from the meaning of parentheses and from the definition of exponents.

3

Final Answer

6b3 6b^3

Key Points to Remember

Essential concepts to master this topic
  • Rule: Multiply coefficients first, then add exponents with same base
  • Technique: 3×2=6 3 \times 2 = 6 and b3×b2×b2=b3+22 b^3 \times b^2 \times b^{-2} = b^{3+2-2}
  • Check: Final answer has one base with combined exponent: 6b3 6b^3

Common Mistakes

Avoid these frequent errors
  • Adding exponents to coefficients
    Don't add the exponents 3, 2, and -2 to the coefficients 3 and 2 = wrong numbers everywhere! Exponents only apply to their bases (the variables), not to the numerical coefficients. Always keep coefficients separate and multiply them normally.

Practice Quiz

Test your knowledge with interactive questions

\( \)

Simplify the following equation:

\( 5^8\times5^3= \)

FAQ

Everything you need to know about this question

Why don't the numbers 3 and 2 get exponents applied to them?

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Great question! In 3b2 3b^2 , the exponent 2 only applies to the variable b, not to the coefficient 3. If we wanted the exponent to apply to both, we'd need parentheses like (3b)2 (3b)^2 .

How do I handle the negative exponent -2?

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Treat negative exponents just like positive ones when adding! So b3×b2×b2 b^3 \times b^2 \times b^{-2} becomes b3+2+(2)=b3+22=b3 b^{3+2+(-2)} = b^{3+2-2} = b^3 . Remember: adding a negative is the same as subtracting!

What's the difference between 3+2-2 and 3×2×(-2)?

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When multiplying terms with the same base, you add the exponents, not multiply them! So it's 3+2+(2)=3 3+2+(-2) = 3 , not 3×2×(2)=12 3 \times 2 \times (-2) = -12 . This is a key exponent rule!

Can I multiply the coefficients 3 and 2 in any order?

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Yes! Multiplication is commutative, so 3×2=2×3=6 3 \times 2 = 2 \times 3 = 6 . You can rearrange and group the terms however makes the problem easier to solve.

How do I check if 6b³ is correct?

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Substitute a simple value like b=2 b = 2 into both the original expression and your answer. Original: 23×3(22)×2(22)=8×12×0.5=48 2^3 \times 3(2^2) \times 2(2^{-2}) = 8 \times 12 \times 0.5 = 48 . Answer: 6(23)=6×8=48 6(2^3) = 6 \times 8 = 48 . They match! ✓

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