Solve the Equation: Simplifying -8(4-x) + 4(2x+5) = 2(7-2x)

Linear Equations with Distributive Property

Solve for X:

8(4x)+4(2x+5)=2(72x) -8(4-x)+4(2x+5)=2(7-2x)

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find X
00:05 Open parentheses properly, multiply by each factor
00:29 Collect like terms
00:46 Arrange the equation so that X is isolated on one side
01:07 Collect like terms
01:15 Isolate X
01:19 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 for X:

8(4x)+4(2x+5)=2(72x) -8(4-x)+4(2x+5)=2(7-2x)

2

Step-by-step solution

To solve this linear equation, we will proceed step by step:

  • Step 1: Apply the distributive property to both sides of the given equation.
  • Step 2: Combine like terms on both sides.
  • Step 3: Rearrange the equation to isolate the variable xx.
  • Step 4: Solve for xx and verify against the choices provided.

Now, let's work through each step:

Step 1: Apply the distributive property:
8(4x)-8(4 - x) becomes 32+8x-32 + 8x and 4(2x+5)4(2x + 5) becomes 8x+208x + 20.
The right side 2(72x)2(7 - 2x) becomes 144x14 - 4x.

This gives us the new equation:
32+8x+8x+20=144x-32 + 8x + 8x + 20 = 14 - 4x.

Step 2: Combine like terms:
On the left side: 32+20+8x+8x=12+16x-32 + 20 + 8x + 8x = -12 + 16x.
On the right side: 144x14 - 4x remains unchanged.

The equation simplifies to:
12+16x=144x-12 + 16x = 14 - 4x.

Step 3: Rearrange the equation to isolate xx.
Add 4x4x to both sides to move the xx terms to one side:
12+16x+4x=14-12 + 16x + 4x = 14.
This simplifies to:
12+20x=14-12 + 20x = 14.

Next, add 12 to both sides to isolate terms with xx:
20x=14+1220x = 14 + 12.
Thus, 20x=2620x = 26.

Step 4: Solve for xx:
Divide by 20:
x=2620=1310x = \frac{26}{20} = \frac{13}{10}.

Therefore, the correct solution is x=1310 x = \frac{13}{10} , which corresponds to choice 3.

3

Final Answer

1310 \frac{13}{10}

Key Points to Remember

Essential concepts to master this topic
  • Distributive Property: Apply -8(4-x) = -32 + 8x carefully to each term
  • Combine Terms: Group like terms: 16x on left, -4x on right
  • Verify Solution: Substitute x=1310 x = \frac{13}{10} back into original equation ✓

Common Mistakes

Avoid these frequent errors
  • Sign errors when distributing negative coefficients
    Don't forget to change signs when distributing negatives like -8(4-x) = -32 - 8x! This gives you -32 - 8x instead of -32 + 8x, leading to completely wrong answers. Always remember: negative times negative equals positive, so -8 × (-x) = +8x.

Practice Quiz

Test your knowledge with interactive questions

\( 5x=1 \)

What is the value of x?

FAQ

Everything you need to know about this question

Why do I keep getting the wrong sign when I distribute -8?

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Remember the rule: negative × negative = positive! When you distribute -8(4-x), you get -8×4 = -32 and -8×(-x) = +8x. The second term becomes positive because you're multiplying two negatives.

How do I keep track of all the x terms?

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Write them clearly on each side first: Left side has +8x and +8x = 16x. Right side has -4x. Then move all x terms to one side: 16x + 4x = 20x.

Can I check my answer without doing all the algebra again?

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Yes! Just substitute x=1310 x = \frac{13}{10} into the original equation. Calculate the left side: -8(4-13/10) + 4(2×13/10+5). Calculate the right side: 2(7-2×13/10). If they're equal, you're correct!

What if I get a different fraction as my answer?

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Double-check your arithmetic! The most common errors are in distributing negatives or combining like terms. Work through each step slowly and verify that 20x = 26, so x = 26/20 = 13/10.

Why is my answer different from the multiple choice options?

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Make sure you've simplified your fraction completely! Also check that you moved all terms correctly: all x terms should end up on one side, all numbers on the other side.

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