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3 years ago

Find x (Will mark brainliest if you are right)

Mathematics

1 answer:

Marizza181 [45]3 years ago

4 0

Answer:

Step-by-step explanation:

(-3x + 2)(45x + 21) + (-4x + 25) = 50

-135x^2 - 63x + 90x + 42 - 4x + 25 = 50

-135x^2 + 23x + 67 = 50

-135x^2 + 23x + 67 - 50 = 0

-135x^2 + 23x + 17 = 0

quadratic formula : x = (-b ± √b^2 - 4ac)/2a

a = -135, b = 23, c = 17

x = -23 ± √23^2 - 4(-135)(17) / (2(-135)

x = (-23 ±√9709 )/ -270

x = 23/270 ± 1 / 270√9709/270

x = 0.4501 or x = - 0.2798 <=== these answers are rounded

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Answer: c. 3.01

Step-by-step explanation:

The test statistic for difference between two population mean (when population standard deviation is known) is given by :

$z=\dfrac{\overline{x}_1-\overline{x}_2}{\sqrt{\dfrac{\sigma_1^2}{n_1}+\dfrac{\sigma_2^2}{n_2}}}$

, where $n_1$ = Size of first sample

$n_2$ = Size of second sample

$\overline{x}_1-\overline{x}_2$ = Difference between two sample mean.

$\sigma_1$ = standard deviation for population 1.

$\sigma_2$ = standard deviation for population 2.

As per given , we have

$n_1=80$

$n_2=60$

$\overline{x}_1=\$6.75$

$\overline{x}_2=\$6.25$

$\sigma_1=\$1$

$\sigma_2=\$0.95$

Substitute these values in formula , we get

$z=\dfrac{6.75-6.25}{\sqrt{\dfrac{(1)^2}{80}+\dfrac{(0.95)^2}{60}}}$

$z=\dfrac{0.50}{\sqrt{0.0275416666667}}$

$z=\dfrac{0.50}{0.165956821694}$

$z=3.0128318613\approx3.01$

Hence, the value of the test statistic is <u>3.01</u>.

Hence, the correct option is c. 3.01 .

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3 years ago

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