Solve (2x+a)(a-4)=2ax+a²-5: Extended Distributive Law Application

Distributive Property with Variable Isolation

Solve the equation using the extended distributive law. Find the relationship between a and x.

(2x+a)(a4)=2ax+a25 (2x+a)(a-4)=2ax+a^2-5

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find A
00:04 Open brackets properly, multiply each factor by each factor
00:28 Calculate the multiplications
00:44 Reduce what we can
01:10 Isolate A
01:18 Calculate the quotients
01:25 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

Solve the equation using the extended distributive law. Find the relationship between a and x.

(2x+a)(a4)=2ax+a25 (2x+a)(a-4)=2ax+a^2-5

2

Step-by-step solution

To solve this problem, we'll follow these steps:

  • Step 1: Expand the expression using the distributive property.
  • Step 2: Compare the coefficients and constant terms to solve for a relationship between a a and x x .

Now, let's work through each step:

Step 1:
The given equation is (2x+a)(a4)=2ax+a25 (2x+a)(a-4) = 2ax + a^2 - 5 . First, expand the left-hand side:

(2x+a)(a4) (2x + a)(a - 4)

Using the distributive property:

  • 2xa=2ax 2x \cdot a = 2ax
  • 2x4=8x 2x \cdot -4 = -8x
  • aa=a2 a \cdot a = a^2
  • a4=4a a \cdot -4 = -4a

Combining these terms gives:

2ax8x+a24a 2ax - 8x + a^2 - 4a

Step 2:
Now, we set the expanded left-hand side equal to the right-hand side from the original equation:

2ax8x+a24a=2ax+a25 2ax - 8x + a^2 - 4a = 2ax + a^2 - 5

Cancel the common terms on both sides:

  • Subtract 2ax 2ax from both sides: 8x4a=5 -8x - 4a = -5
  • Subtract a2 a^2 from both sides: No change needed since both sides already equal.

The equation becomes:

8x4a=5 -8x - 4a = -5

Solving for a a :

Add 4a 4a to both sides:

8x=4a5 -8x = 4a - 5

Divide each term by 4 to solve for a a :

a=2x+54 a = -2x + \frac{5}{4}

Expressing in a simpler equivalent format, we have:

a=2x+114 a = -2x + 1\frac{1}{4}

Therefore, we find the relationship between a a and x x to be a=1142x a = 1\frac{1}{4} - 2x .

3

Final Answer

a=1142x a=1\frac{1}{4}-2x

Key Points to Remember

Essential concepts to master this topic
  • Expansion: Apply distributive property to multiply each term systematically
  • Technique: Cancel identical terms like 2ax 2ax from both sides
  • Check: Substitute a=1142x a = 1\frac{1}{4} - 2x back into original equation ✓

Common Mistakes

Avoid these frequent errors
  • Canceling terms incorrectly when expanding
    Don't subtract 2ax 2ax from only one side = unbalanced equation! This leaves wrong terms and gives incorrect relationships. Always cancel identical terms from both sides simultaneously.

Practice Quiz

Test your knowledge with interactive questions

It is possible to use the distributive property to simplify the expression below?

What is its simplified form?

\( (ab)(c d) \)

\( \)

FAQ

Everything you need to know about this question

Why do I need to expand the left side first?

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Expanding (2x+a)(a4) (2x+a)(a-4) shows all individual terms clearly. Without expansion, you can't identify which terms cancel out on both sides of the equation.

What does it mean to 'cancel identical terms'?

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When both sides have the exact same term like 2ax 2ax or a2 a^2 , you can subtract them from both sides. This simplifies the equation without changing the solution.

How do I know which variable to solve for?

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The problem asks for the relationship between a and x. Since the correct answer expresses a in terms of x, that's what we solve for!

Can I rearrange the final answer differently?

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Yes! a=1142x a = 1\frac{1}{4} - 2x can also be written as a=542x a = \frac{5}{4} - 2x or a=2x+1.25 a = -2x + 1.25 . All forms are mathematically equivalent.

What if I get a different relationship like x in terms of a?

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While algebraically valid, check the answer choices! The correct format here is a in terms of x, so rearrange your equation to match the expected form.

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