Simplify (x/3-4)² + x(√8x/3+2)(√8x/3-2): Complete Solution

Algebraic Expressions with Multiple Formulas

(x34)2+x(8x3+2)(8x32)=? (\frac{x}{3}-4)^2+x(\frac{\sqrt{8x}}{3}+2)(\frac{\sqrt{8x}}{3}-2)=\text{?}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Simply
00:07 We'll use the shortened multiplication formulas to open the parentheses
00:20 Shortened multiplication formulas for this case
00:24 We'll use this formula in our exercise
00:39 Square both numerator and denominator
00:44 Calculate 4 squared
00:51 Square both numerator and denominator
01:05 Open parentheses properly, multiply by each factor
01:14 Collect terms
01:31 Simplify what we can
01:36 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

(x34)2+x(8x3+2)(8x32)=? (\frac{x}{3}-4)^2+x(\frac{\sqrt{8x}}{3}+2)(\frac{\sqrt{8x}}{3}-2)=\text{?}

2

Step-by-step solution

Let's solve this problem by simplifying each component separately:

First, simplify (x34)2(\frac{x}{3} - 4)^2 using the square of a difference formula:

(x34)2=(x3)22×x3×4+42 (\frac{x}{3} - 4)^2 = \left(\frac{x}{3}\right)^2 - 2 \times \frac{x}{3} \times 4 + 4^2 This becomes:

=x298x3+16 = \frac{x^2}{9} - \frac{8x}{3} + 16

Next, simplify x(8x3+2)(8x32)x(\frac{\sqrt{8x}}{3} + 2)(\frac{\sqrt{8x}}{3} - 2) using the difference of squares formula:

(8x3+2)(8x32)=(8x3)222 (\frac{\sqrt{8x}}{3} + 2)(\frac{\sqrt{8x}}{3} - 2) = \left(\frac{\sqrt{8x}}{3}\right)^2 - 2^2 Simplify further:

=8x94 = \frac{8x}{9} - 4

Including the factor of xx, we have:

x(8x94)=8x294x x \left(\frac{8x}{9} - 4\right) = \frac{8x^2}{9} - 4x

Combine the results from both parts:

(x298x3+16)+(8x294x) \left(\frac{x^2}{9} - \frac{8x}{3} + 16\right) + \left(\frac{8x^2}{9} - 4x\right)

Simplify by combining like terms:

=x29+8x298x34x+16=x2(8x3+4x)+16=x2(8x+12x3)+16=x220x3+16 = \frac{x^2}{9} + \frac{8x^2}{9} - \frac{8x}{3} - 4x + 16 = x^2 - \left(\frac{8x}{3} + 4x\right) + 16 = x^2 - \left(\frac{8x + 12x}{3}\right) + 16 = x^2 - \frac{20x}{3} + 16

Therefore, after simplifying, the expression becomes x220x3+16\boldsymbol{x^2 - \frac{20x}{3} + 16}.

The final solution is: x220x3+16 x^2 - \frac{20x}{3} + 16 .

3

Final Answer

x2623x+16 x^2-6\frac{2}{3}x+16

Key Points to Remember

Essential concepts to master this topic
  • Formula Application: Use (a-b)² and (a+b)(a-b) formulas correctly
  • Technique: Simplify (x3)2=x29 (\frac{x}{3})^2 = \frac{x^2}{9} and combine like terms
  • Check: Verify x29+8x29=x2 \frac{x^2}{9} + \frac{8x^2}{9} = x^2 when combining coefficients ✓

Common Mistakes

Avoid these frequent errors
  • Forgetting to distribute the x factor correctly
    Don't calculate (8x3+2)(8x32) (\frac{\sqrt{8x}}{3} + 2)(\frac{\sqrt{8x}}{3} - 2) and forget the x multiplier = missing terms! This gives 8x94 \frac{8x}{9} - 4 instead of 8x294x \frac{8x^2}{9} - 4x . Always multiply the entire result by any factors outside the parentheses.

Practice Quiz

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Choose the expression that has the same value as the following:

\( (x-y)^2 \)

FAQ

Everything you need to know about this question

Why do we use the difference of squares formula here?

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The expression (8x3+2)(8x32) (\frac{\sqrt{8x}}{3} + 2)(\frac{\sqrt{8x}}{3} - 2) has the form (a + b)(a - b), which always equals a2b2 a^2 - b^2 . This saves time compared to expanding manually!

How do I combine fractions with different denominators like 8x/3 and 4x?

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Convert to the same denominator first: 4x=12x3 4x = \frac{12x}{3} , so 8x3+12x3=20x3 \frac{8x}{3} + \frac{12x}{3} = \frac{20x}{3} . Always find a common denominator before adding or subtracting fractions.

What if I get confused with all the x² terms?

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Group them step by step: x29+8x29 \frac{x^2}{9} + \frac{8x^2}{9} first. Since they have the same denominator, add the numerators: 9x29=x2 \frac{9x^2}{9} = x^2 . Take it one step at a time!

Why does the final answer look different from the given options?

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The explanation shows x220x3+16 x^2 - \frac{20x}{3} + 16 , but the correct answer is x2623x+16 x^2 - 6\frac{2}{3}x + 16 . Note that 203=623 \frac{20}{3} = 6\frac{2}{3} , so they're the same value in different forms!

How do I avoid making arithmetic errors with fractions?

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Work one operation at a time and write each step clearly. Double-check fraction arithmetic: 8x3+4x=8x3+12x3=20x3 \frac{8x}{3} + 4x = \frac{8x}{3} + \frac{12x}{3} = \frac{20x}{3} . Going slowly prevents mistakes!

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