Ask question

Ask question

All categories

4 years ago

6

Factor the polynomial completetly 21b2-40b-21

1 answer:

ch4aika [34]4 years ago

3 0

First we note symmetry in the expression's coefficients.
We also note that 7*3=21, and 7+3=10.

From the rational roots theorem, we are tempted to try with 3 and 7 as coefficients of the factors.

Try
(7b+3)(3b+7)=21b^2+(49+9)b+21
By switching the sign of 3b+7 to 3b-7, we get the signs right, to check:
(7b+3)(3b-7)=21b^2+(9-49)b-21=21b^2-40b-21 ....right!

So
(7b+3)(3b-7)=21b^2-40b-21

You might be interested in

A veterinarian wants to know if pit bulls or golden retrievers have a higher incidence of tooth decay at the age of three. The v

BigorU [14]

Answer: B) [-0.0332,0.1332]

Step-by-step explanation: <u>Confidence</u> <u>Interval</u> is an interval where we can be a percentage sure the true mean is.

The confidence interval for a difference in population proportion is calculated following these steps:

First, let's find population proportion for each population:

$p_{1}=\frac{30}{120}=0.25$

$p_{2}=\frac{32}{160}=0.2$

Second, calculate standard deviation for each proportion:

$\sigma_{1}=\sqrt{\frac{0.25(0.75)}{120} } = 0.0395$

$\sigma_{2}=\sqrt{\frac{0.2(0.8)}{160} } = 0.0316$

Now, we calculate standard error for difference:

$SE=\sqrt{\sigma_{1}^{2}+\sigma_{2}^{2}}$

$SE=\sqrt{0.0395^{2}+0.0316^{2}}$

SE = 0.0505

The z-score for a 90% CI is 1.645.

Then, confidence interval is

$p_{1}-p_{2}$ ± z-score.SE

$0.25-0.2$ ± $1.645(0.0505)$

0.05 ± 0.0831

The limits of this interval are:

inferior: 0.05 - 0.0831 = $-0.0332$

superior: 0.05 + 0.0831 = 0.1332

The 90% confidence interval for the difference in the population proportion of pit pulls and golden retrievers is $[-0.0332,0.1332]$ .

8 0

3 years ago

5) The diagram below shows a ramp connecting the ground

nlexa [21]

Step-by-step explanation:

///////hope it helps:)

8 0

3 years ago

7 x 1/5 as a mixed number

iVinArrow [24]

Answer:

It's 15/7

Step-by-step explanation:

7 0

3 years ago

Read 2 more answers

Seven years ago, Raymond purchased a $197,000 home with a 30-year mortgage at 4.15%. Having recently lost his job, he can no lon

Bumek [7]

Answer: does anybody know?

Step-by-step explanation:

8 0

3 years ago

Read 2 more answers

Find the slope of the line containing the pair of points.<br> (2, -9) and (12,6)

dusya [7]

Answer:

slope = $\frac{3}{2}$

Step-by-step explanation:

calculate the slope m using the slope formula

m = $\frac{y_{2}-y_{1} }{x_{2}-x_{1} }$

with (x₁, y₁ ) = (2, - 9 ) and (x₂, y₂ ) = (12, 6 )

m = $\frac{6-(-9)}{12-2}$ = $\frac{6+9}{10}$ = $\frac{15}{10}$ = $\frac{3}{2}$

5 0

2 years ago