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40 votes
40 votes
3x^2+12x=7 Complete the square to solve

User Sphereinabox
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2 Answers

12 votes
12 votes

Answer:

Explanation:

3x^2+12x=7 Complete the square to solve-example-1
3x^2+12x=7 Complete the square to solve-example-2
User Igor Rodriguez
by
3.1k points
12 votes
12 votes

Answer:

x = - 2 ±
\sqrt{(19)/(3) }

Explanation:

3x² + 12x = 7 ← factor out 3 from each term on the left side

3(x² + 4x) = 7

to complete the square

add/ subtract ( half the coefficient of the x- term)² to x² + 4x

3(x² + 2(2)x + 4 - 4) = 7

3(x + 2)² - 12 = 7 ( add 12 to both sides )

3(x + 2)² = 19 ( divide both sides by 3 )

(x + 2)² =
(19)/(3) ( take square root of both sides )

x + 2 = ±
\sqrt{(19)/(3) } ( subtract 2 from both sides )

x = - 2 ±
\sqrt{(19)/(3) }

User Michael Mikhjian
by
2.7k points