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4 years ago

Simplify (y + 9)(y - 9). А у2 B у2 - 18 C y2 - 81 D у2 + 81

Mathematics

2 answers:

mestny [16]4 years ago

8 0

Answer:

Answer is y^2-81

Step-by-step explanation:

Varvara68 [4.7K]4 years ago

4 0

Answer:

Step-by-step explanation:

According to formula

(a+b)(a-b)=a²-b²

(y+9)(y-9)

=y²-(9)²

=y²-81

You might be interested in

A bank sampled its customers to determine the proportion of customers who use their debit card at least once each month. A sampl

Zinaida [17]

Answer:

(0.084,0.396)

Step-by-step explanation:

The 99% confidence interval for the proportion of customers who use debit card monthly can be constructed as

$p-z_{\frac{\alpha }{2}} \sqrt{\frac{pq}{n} }$

$p=\frac{x}{n}$

$p=\frac{12}{50}$

$p=0.24$

$q=1-p=1-0.24=0.76$

$\frac{\alpha }{2} =\frac{\0.01 }{2}=0.005$

$p-z_{\frac{\alpha }{2}} \sqrt{\frac{pq}{n} }$

$0.24-z_{0.005} \sqrt{\frac{0.24*0.76}{50} }$

$0.24-2.58(0.0604)$

$0.24-0.155832$

By rounding to three decimal places we get,

$0.084$

The 99% confidence interval for the proportion of customers who use debit card monthly is (0.084,0.396).

3 0

3 years ago

I need to find the perimeter and area of the regular polygon.

mezya [45]

The area of a polygon is given by the formula Area = ap/2 where a is the length of the apothem and p is the perimeter. The apothem is a line from the center of the polygon perpendicular to a side.

Depending on the formula you know, you can find the length of a side in 1 of 2 ways.

The first way uses a triangle. Using the radius of the polygon you can create 8 congruent triangles. The center angle will be 360 / 8 = 45 and two side lengths of 20. You can find the length of the base using the law of cosines.

c^2 = 20^2 + 20^2 - 2(20)(20)(cos 45)
c^2 = 400 + 400 - 800(cos 45)
c^2 = 800 - 800(cos 45)
c = sqrt(800 - 800(cos 45)
c = 15.31

The second way is to use this formula:
r = s / (2 sin(180 / n))
20 = s / (2 sin(180/8)
(20)(2)sin(22.5) = s
(40)sin(22.5) = s
s = 15.31

We need to calculate the perimeter. As there are 8 sides (8)(15.31) = 122.48
Now we need to calculate the apothem using

a = S / (2 tan (180 / n)
a = 15.31 / (2 tan (180 / 8))
a = 18.48

Now solve for the area

Area = ap/2
Area = (18.48)(122.48)/2
Area = 1131.72

perimeter = 122.48
area = 1131.72

7 0

3 years ago

Question 4<br> What is the value of x? n10 / n12 = n*<br> need answer will mark brainlist

Crazy boy [7]

Answer:

Step-by-step explanation:

$\frac{n^{10}}{n^{12}}=n^x\\n^{10-12}=n^x\\n^{-2}=n^x\\x=-2$

8 0

3 years ago

The data below are the ages and systolic blood pressures (measured in millimeters of mercury) of 9 randomly selected adults. Wha

seraphim [82]

Answer:

$\sum_{i=1}^n x_i =459$

$\sum_{i=1}^n y_i =1227$

$\sum_{i=1}^n x^2_i =24059$

$\sum_{i=1}^n y^2_i =168843$

$\sum_{i=1}^n x_i y_i =63544$

With these we can find the sums:

$S_{xx}=\sum_{i=1}^n x^2_i -\frac{(\sum_{i=1}^n x_i)^2}{n}=24059-\frac{459^2}{9}=650$

$S_{xy}=\sum_{i=1}^n x_i y_i -\frac{(\sum_{i=1}^n x_i)(\sum_{i=1}^n y_i)}{n}=63544-\frac{459*1227}{9}=967$

And the slope would be:

$m=\frac{967}{650}=1.488$

Nowe we can find the means for x and y like this:

$\bar x= \frac{\sum x_i}{n}=\frac{459}{9}=51$

$\bar y= \frac{\sum y_i}{n}=\frac{1227}{9}=136.33$

And we can find the intercept using this:

$b=\bar y -m \bar x=136.33-(1.488*51)=60.442$

So the line would be given by:

$y=1.488 x +60.442$

And then the best predicted value of y for x = 41 is:

$y=1.488*41 +60.442 =121.45$

Step-by-step explanation:

For this case we assume the following dataset given:

x: 38,41,45,48,51,53,57,61,65

y: 116,120,123,131,142,145,148,150,152

For this case we need to calculate the slope with the following formula:

$m=\frac{S_{xy}}{S_{xx}}$

Where:

$S_{xy}=\sum_{i=1}^n x_i y_i -\frac{(\sum_{i=1}^n x_i)(\sum_{i=1}^n y_i)}{n}$

$S_{xx}=\sum_{i=1}^n x^2_i -\frac{(\sum_{i=1}^n x_i)^2}{n}$

So we can find the sums like this:

$\sum_{i=1}^n x_i =459$

$\sum_{i=1}^n y_i =1227$

$\sum_{i=1}^n x^2_i =24059$

$\sum_{i=1}^n y^2_i =168843$

$\sum_{i=1}^n x_i y_i =63544$

With these we can find the sums:

$S_{xx}=\sum_{i=1}^n x^2_i -\frac{(\sum_{i=1}^n x_i)^2}{n}=24059-\frac{459^2}{9}=650$

$S_{xy}=\sum_{i=1}^n x_i y_i -\frac{(\sum_{i=1}^n x_i)(\sum_{i=1}^n y_i)}{n}=63544-\frac{459*1227}{9}=967$

And the slope would be:

$m=\frac{967}{650}=1.488$

Nowe we can find the means for x and y like this:

$\bar x= \frac{\sum x_i}{n}=\frac{459}{9}=51$

$\bar y= \frac{\sum y_i}{n}=\frac{1227}{9}=136.33$

And we can find the intercept using this:

$b=\bar y -m \bar x=136.33-(1.488*51)=60.442$

So the line would be given by:

$y=1.488 x +60.442$

And then the best predicted value of y for x = 41 is:

$y=1.488*41 +60.442 =121.45$

3 0

3 years ago

I need help plsssss zzzzz

Ganezh [65]

Answer:

right angle

if there is a square in the corner, it is ALWAYS a right angle

3 0

2 years ago