When a sample size is greater than 10, the standard deviation of the sample is an accurate predictor of the population standard
1 answer:
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Answer:
x ≈ - 4.12 , x ≈ 0.12
Step-by-step explanation:
Given
2x² + 8x - 1 = 0 ( add 1 to both sides )
2x² + 8x = 1 ← factor out 2 on the left side
2(x² + 4x) = 1
To complete the square
add/ subtract (half the coefficient of the x- term )² to x² + 4x
2(x² + 2(2)x + 4 - 4) = 1, that is
2(x + 2)² - 8 = 1 ( add 8 to both sides )
2(x + 2)² = 9 ( divide both sides by 2 )
(x + 2)² = ( take the square root of both sides )
x + 2 = ± = ±
= ±
( subtract 2 from both sides )
x = - 2 ± 1.5 , thus
x = - 2 - 1.5 ≈ - 4.12 ( to 2 dec. places )
x = - 2 + 1.5 ≈ 0.12 ( to 2 dec. places )