Solve the Fraction Puzzle: Simplify 85x×y³/5y⁴x³ × 9xy/3yx²

Multiplying Rational Expressions with Negative Exponents

Solve:

85xy35y4x39xy3yx2= \frac{85x\cdot y^3}{5y^4x^3}\cdot\frac{9xy}{3yx^2}=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Simplify the following problem
00:03 Let's reduce wherever possible
00:07 Break down 85 into factors of 17 and 5
00:10 Break down 9 into factors of 3 and 3
00:13 Make sure to multiply the numerator by the numerator and the denominator by the denominator
00:23 Let's reduce wherever possible
00:43 Calculate 17 x 3
00:47 When multiplying powers with equal bases
00:50 The power of the result equals the sum of powers
00:53 We'll apply this formula to our exercise and then proceed to add the powers together
01:14 When dividing powers with equal bases
01:17 The power of the result equals the difference of powers
01:21 We'll apply this formula to our exercise and then proceed to subtract the powers
01:41 This is the solution

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Solve:

85xy35y4x39xy3yx2= \frac{85x\cdot y^3}{5y^4x^3}\cdot\frac{9xy}{3yx^2}=

2

Step-by-step solution

To solve this problem, we'll simplify each part of the given expression step by step:

Original expression:
85xy35y4x39xy3yx2\frac{85x \cdot y^3}{5y^4x^3} \cdot \frac{9xy}{3yx^2}.

Let's simplify the first fraction:
85xy35y4x3\frac{85x \cdot y^3}{5y^4x^3}.

  • Divide the coefficients: 855=17\frac{85}{5} = 17.
  • Apply the quotient rule of exponents:
    xx3=x13=x2\frac{x}{x^3} = x^{1-3} = x^{-2} and y3y4=y34=y1\frac{y^3}{y^4} = y^{3-4} = y^{-1}.
  • This simplifies to: 17x2y117x^{-2}y^{-1}.

Now, simplify the second fraction:
9xy3yx2\frac{9xy}{3yx^2}.

  • Divide the coefficients: 93=3\frac{9}{3} = 3.
  • Cancel the y y : yy=1\frac{y}{y} = 1.
  • Apply the quotient rule of exponents: xx2=x12=x1\frac{x}{x^2} = x^{1-2} = x^{-1}.
  • This simplifies to: 3x13x^{-1}.

Multiply the simplified expressions:
(17x2y1)(3x1)(17x^{-2}y^{-1})\cdot (3x^{-1}).

  • Combine the coefficients: 173=5117 \cdot 3 = 51.
  • Apply the product rule for x x : x2x1=x21=x3x^{-2} \cdot x^{-1} = x^{-2-1} = x^{-3}.
  • For y y , simply note: y1y^{-1}.

Thus, the simplified expression is: 51x3y1 51x^{-3}y^{-1} .

3

Final Answer

51x3y1 51x^{-3}y^{-1}

Key Points to Remember

Essential concepts to master this topic
  • Quotient Rule: When dividing powers, subtract exponents: xaxb=xab \frac{x^a}{x^b} = x^{a-b}
  • Technique: Simplify coefficients first: 855=17 \frac{85}{5} = 17 , then 93=3 \frac{9}{3} = 3
  • Check: Verify by substituting x=1, y=1: 51(1)3(1)1=51 51(1)^{-3}(1)^{-1} = 51

Common Mistakes

Avoid these frequent errors
  • Adding instead of subtracting exponents when dividing
    Don't add exponents when dividing like xx3=x1+3=x4 \frac{x}{x^3} = x^{1+3} = x^4 ! This gives completely wrong answers because you're multiplying instead of dividing. Always subtract the bottom exponent from the top: xx3=x13=x2 \frac{x}{x^3} = x^{1-3} = x^{-2} .

Practice Quiz

Test your knowledge with interactive questions

Simplify the following equation:

\( \)\( 4^5\times4^5= \)

FAQ

Everything you need to know about this question

What does a negative exponent mean?

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A negative exponent means "one over" the positive version. For example, x3=1x3 x^{-3} = \frac{1}{x^3} and y1=1y y^{-1} = \frac{1}{y} .

Why don't we convert negative exponents to fractions in the final answer?

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Both forms are correct! 51x3y1 51x^{-3}y^{-1} and 51x3y \frac{51}{x^3y} mean the exact same thing. Negative exponent form is often preferred in algebra.

How do I multiply expressions with the same base?

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Use the product rule: add the exponents when multiplying. For example, x2x1=x2+(1)=x3 x^{-2} \cdot x^{-1} = x^{-2+(-1)} = x^{-3} .

Can I cancel variables that appear in both fractions?

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Yes! When you see yy \frac{y}{y} , this equals 1 and disappears. But be careful with different powers - y3y4 \frac{y^3}{y^4} becomes y1 y^{-1} , not zero!

What's the easiest way to avoid mistakes?

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Work step by step: First simplify coefficients (85÷5=17, 9÷3=3), then handle each variable separately using exponent rules. Don't try to do everything at once!

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