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Solve by completing the square
3x2 + x - 2 = 0​

User HinneLinks
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1 Answer

4 votes

Answer:

x = 2/3 or x = -1

Step-by-step explanation by completing the square:

Solve for x:

3 x^2 + x - 2 = 0

Divide both sides by 3:

x^2 + x/3 - 2/3 = 0

Add 2/3 to both sides:

x^2 + x/3 = 2/3

Add 1/36 to both sides:

x^2 + x/3 + 1/36 = 25/36

Write the left hand side as a square:

(x + 1/6)^2 = 25/36

Take the square root of both sides:

x + 1/6 = 5/6 or x + 1/6 = -5/6

Subtract 1/6 from both sides:

x = 2/3 or x + 1/6 = -5/6

Subtract 1/6 from both sides:

Answer: x = 2/3 or x = -1

User Dannybucks
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