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soldier1979 [14.2K]
4 years ago
14

Without solving the equation, determine the nature of the roots of x2 - 2 x - 8 = 0.

Mathematics
1 answer:
ad-work [718]4 years ago
3 0
Evaluate using the discriminant (the part of the quadratic equation under the square root sign) b²-4ac
In your equation, a=1, b=(-2), and c=(-8)...substitute their values into the discriminant:
(-2)²-4(1)(-8)
4+32 = 36

The value is positive, therefore the equation has two real roots.
It's a perfect square (√36=6) so the roots are rational
Answer: two real, rational roots

(If the result was a negative number, the system would have two irrational roots. If the result was zero, the system would have a <em>double root </em>(one value repeated twice - when graphed, the vertex of the parabola falls on the x-axis)∨<em />
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• A researcher claims that less than 40% of U.S. cell phone owners use their phone for most of their online browsing. In a rando
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Answer:

We failed to reject H₀

Z > -1.645

-1.84 > -1.645

We failed to reject H₀

p > α

0.03 > 0.01

We do not have significant evidence at a 1% significance level to claim that less than 40% of U.S. cell phone owners use their phones for most of their online browsing.

Step-by-step explanation:

Set up hypotheses:

Null hypotheses = H₀: p = 0.40

Alternate hypotheses = H₁: p < 0.40

Determine the level of significance and Z-score:

Given level of significance = 1% = 0.01

Since it is a lower tailed test,

Z-score = -2.33 (lower tailed)

Determine type of test:

Since the alternate hypothesis states that less than 40% of U.S. cell phone owners use their phone for most of their online browsing, therefore we will use a lower tailed test.

Select the test statistic:  

Since the sample size is quite large (n > 30) therefore, we will use Z-distribution.

Set up decision rule:

Since it is a lower tailed test, using a Z statistic at a significance level of 1%

We Reject H₀ if Z < -1.645

We Reject H₀ if p ≤ α

Compute the test statistic:

$ Z =  \frac{\hat{p} - p}{ \sqrt{\frac{p(1-p)}{n} }}  $

$ Z =  \frac{0.31 - 0.40}{ \sqrt{\frac{0.40(1-0.40)}{100} }}  $

$ Z =  \frac{- 0.09}{ 0.048989 }  $

Z = - 1.84

From the z-table, the p-value corresponding to the test statistic -1.84 is

p = 0.03288

Conclusion:

We failed to reject H₀

Z > -1.645

-1.84 > -1.645

We failed to reject H₀

p >  α

0.03 > 0.01

We do not have significant evidence at a 1% significance level to claim that less than 40% of U.S. cell phone owners use their phones for most of their online browsing.

8 0
3 years ago
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