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1 year ago

What are the solution(s) to the quadratic equation 9x² = 4?

Mathematics

2 answers:

UkoKoshka [18]1 year ago

6 0

Answer:

x = ± $\frac{2}{3}$

Step-by-step explanation:

9x² = 4 ( divide both sides by 9 )

x² = $\frac{4}{9}$ ( take square root of both sides )

x = ± $\sqrt{\frac{4}{9} }$ = ± $\frac{\sqrt{4} }{\sqrt{9} }$ = ± $\frac{2}{3}$

x = - $\frac{2}{3}$ , x = $\frac{2}{3}$

vagabundo [1.1K]1 year ago

5 0

Answer:

x= 2/3, -2/3

Step-by-step explanation:

9x² = 4

To solve this quadratic, divide each side by 9

x^2 = 4/9

Take the square root of each side

sqrt(x^2) = sqrt(4/9)

x = ±2/3

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Answer:

a) $n=\frac{0.5(1-0.5)}{(\frac{0.02}{1.96})^2}=2401$

And rounded up we have that n=2401

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And we see that if we have previous info about p the sample size varies a lot.

Step-by-step explanation:

Previous concepts

A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".

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Solution to the problem

In order to find the critical value we need to take in count that we are finding the interval for a proportion, so on this case we need to use the z distribution. Since our interval is at 95% of confidence, our significance level would be given by $\alpha=1-0.95=0.05$ and $\alpha/2 =0.025$ . And the critical value would be given by:

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Part a

The margin of error for the proportion interval is given by this formula:

$ME=z_{\alpha/2}\sqrt{\frac{\hat p (1-\hat p)}{n}}$ (a)

And on this case we have that $ME =\pm 0.02$ and we are interested in order to find the value of n, if we solve n from equation (a) we got:

$n=\frac{\hat p (1-\hat p)}{(\frac{ME}{z})^2}$ (b)

Since we don't have prior information about the population proportion we can use ase estimator $\hat p =0.5$ . And replacing into equation (b) the values from part a we got:

$n=\frac{0.5(1-0.5)}{(\frac{0.02}{1.96})^2}=2401$

And rounded up we have that n=2401

Part b

For thi case the estimator for p is $\hat p =0.07$

$n=\frac{0.07(1-0.07)}{(\frac{0.02}{1.96})^2}=625.22$

And rounded up we have that n=626

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