Answer:
Confidence interval is 128±2.326 days (between 125.674 days and 130.326 days) in 90% confidence level
Step-by-step explanation:
Confidence interval can be calculated as M±ME where
- M is the average pregnancy days of smoking women and
- ME is the margin of error in 90% confidence level.
Margin of Error in 90% confidence level can be calculated using the formula:
ME=
where
- z is the z-value in 90% confidence level (1.645)
- s is the standard deviation of pregnancy length (16)
- N is the sample size (128)
putting these numbers in the formula, we get:
ME=
=2.326
then confidence interval is 128±2.326 ( between 125.674 and 130.326 ) in 90% confidence level
1. 3x² + 12x - 15 = 0
x = <u>-(12) +/- √((12)² - 4(3)(-15))</u>
2(3)
x = <u>-12 +/- √(144 + 180)</u>
6
x = <u>-12 +/- √(324)
</u> 6<u>
</u> x = <u>-12 +/- 18 </u>
6
x = -2 <u>+</u> 3
x = -2 + 3 x = -2 - 3
x = 1 x = -5
--------------------------------------------------------------------------------------------
2. 5x² + 11x + 2 = 0
x = <u>-(11) +/- √((11)² - 4(5)(2))</u>
2(5)
x = <u>-11 +/- √(121 - 40)</u>
10
x = <u>-11 +/- √(81)
</u> 10
x = <u>-11 +/- 9</u>
10
x = -1¹/₁₀ <u>+</u> ⁹/₁₀
x = -1¹/₁₀ + ⁹/₁₀ x = -1¹/₁₀ - ⁹/₁₀
x = ¹/₅ x = -2
--------------------------------------------------------------------------------------------
3. 2x² - 11x + 14 = 0
x = <u>-(-11) +/- √((-11)² - 4(2)(14))</u>
2(3)
x = <u>11 +/- √(121 - 102)</u>
6
x = <u>11 +/- √(9)</u>
6
x = <u>11 +/- 3</u>
6
x = 1⁵/₆ <u>+</u> ¹/₂
x = 1⁵/₆ + ¹/₂ x = 1⁵/₆ - ¹/₂
x = 2¹/₃ x = 1¹/₃
--------------------------------------------------------------------------------------------
4. 2x² - x - 15 = 0
x = <u>-(-1) +/- √((-1)² - 4(2)(-15))</u>
2(2)
x = <u>1 +/- √(1 + 120)</u>
4
x = <u>1 +/- √(121)</u>
4
x = <u>1 +/- 11</u>
4
x = ¹/₄ <u>+</u> 2³/₄
x = ¹/₄ + 2³/₄ x = ¹/₄ - 2³/₄
x = 3 x = 2¹/₂
<u />
Answer:
y=-2x+2
Step-by-step explanation:
If you bring the 4x to the other side by subtracting it, you will have 2y=-4x+8
then divide by the 2 to get y=-2x=4
then you substitute the 5 in for y and the -1 in for x. multiply and then subtract
Answer:
No solution
Step-by-step explanation:
3+6=9
3-4=-1
9 doesn't equal -1 therefore no solution.
Answer:
x = 8
Step-by-step explanation:
If the number 212x5 is a multiple of 3, the sum of the digits needs to be a multiple of 3, so we have:
2 + 1 + 2 + x + 5 = 10 + x
The value of x can be 2, 5 or 8
If the number is a multiple of 11, we have to calculate the first number minus the second, plus the third, minus the fourth... and so on, and the result needs to be a multiple of 11. So we have:
2 - 1 + 2 - x + 5 = 8 - x
x needs to be 8, so we have 8 - 8 = 0, that is a multiple of 11.
So the value of x is 8.
