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Linear equationsAlgebraMiddle schoolabout 0:47

Solve 8x + 12 = -4x - 9: animated lesson

A narrated, step-by-step linear equations video lesson with captions. Final answer: x = -7/4 ≈ -1.75.

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Video with a synthetic English voice and captions. Pick another language for subtitles in that language, or open the interactive version.

Video narrated by a synthetic voice (Piper TTS, en_US-ljspeech-high voice (LJ Speech dataset, public domain)); the steps come from our maths engine and the answer was checked independently. Download MP4 (0.3 MB) · Captions (WebVTT)

Steps on screen

1. The problem
Solving an equation
$8~ x+12 = -4~ x-9$
2. Step by step
1. $8~ x+12 = -4~ x-9$
  Start with the equation
2. $12x + 12 = -9$
  Add 4x to both sides
3. $12x = -21$
  Subtract 12 from both sides
4. $x = \frac{-21}{12} = -\frac{7}{4}$
  Divide both sides by 12
3. The answer
$x = -\frac{7}{4} \approx -1.75$
x = -7/4 ≈ -1.75
4. Check
- x = -1.75: left side = -2, right side = -2 ✓

Transcript

The problem. Here is the problem: 8x plus 12 equals negative 4x minus 9. A linear equation in x: isolate x using inverse operations.

Step by step. Start with the equation. Add 4x to both sides. Subtract 12 from both sides. Divide both sides by 12.

The answer. So the answer is x equals negative 7 over 4 approximately negative 1.75. Doing the same operation to both sides keeps the equation balanced. Undoing addition, then multiplication, leaves x alone.

Check. x equals negative 1.75: left side equals negative 2, right side equals negative 2, which checks out.

About linear equations

Solve one-variable linear equations, including ones with brackets and fractions, and check the solution.

Solve 8x + 12 = -4x - 9: Animated Step-by-Step Lesson