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Linear equationsAlgebraMiddle schoolabout 0:44

Solve for x: -4x - 9 = 20: animated lesson

A narrated, step-by-step linear equations video lesson with captions. Final answer: x = -29/4 ≈ -7.25.

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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
$-4~ x-9 = 20$
2. Step by step
1. $-4~ x-9 = 20$
  Start with the equation
2. $-4x = 29$
  Add 9 to both sides
3. $x = \frac{29}{-4} = -\frac{29}{4}$
  Divide both sides by -4
3. The answer
$x = -\frac{29}{4} \approx -7.25$
x = -29/4 ≈ -7.25
4. Check
- x = -7.25: left side = 20, right side = 20 ✓

Transcript

The problem. Here is the problem: negative 4x minus 9 equals 20. A linear equation in x: isolate x using inverse operations.

Step by step. Start with the equation. Add 9 to both sides. Divide both sides by negative 4.

The answer. So the answer is x equals negative 29 over 4 approximately negative 7.25. Doing the same operation to both sides keeps the equation balanced. Undoing addition, then multiplication, leaves x alone.

Check. x equals negative 7.25: left side equals 20, right side equals 20, which checks out.

About linear equations

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

Solve for x: -4x - 9 = 20: Animated Step-by-Step Lesson