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ANTONII [103]
3 years ago
9

Factor 81x²-25. Remember there is no middle term. This is a sum and difference of 2 squares.

Mathematics
1 answer:
natulia [17]3 years ago
5 0

Hey there!!

Basic formula :

... a² - b² = ( a + b ) ( a - b )

Equation given :

... 81x² - 25

... ( 9x )² - ( 5 )²

... ( 9x + 5 ) ( 9x - 5 )

Hope it helps!!

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The grade point averages (GPA) for 12 randomly selected college students are shown on the right. Complete parts (a) through (c)
Ilya [14]

Answer:

\bar X =\frac{2.3+3.1+2.8+1.7+0.9+4+2.1+1.2+3.6+0.2+2.4+3.2}{12}=2.29

s=1.09

Step-by-step explanation:

For this case we have the following data given:

2.3 3.1 2.8

1.7 0.9 4.0

2.1 1.2 3.6

0.2 2.4 3.2

Since the data are assumedn normally distributed we can find the standard deviation with the following formula:

\sigma =\sqrt{\frac{\sum_{i=1}^n (X_i -\bar X)^2}{n}}

And we need to find the mean first with the following formula:

\bar X = \frac{\sum_{i=1}^n X_i}{n}

And replacing we got:

\bar X =\frac{2.3+3.1+2.8+1.7+0.9+4+2.1+1.2+3.6+0.2+2.4+3.2}{12}=2.29

And then we can calculate the deviation and we got:

s=1.09

7 0
2 years ago
Read 2 more answers
When the solution of x2 − 9x − 6 is expressed as 9 plus or minus the square root of r, all over 2, what is the value of r? x equ
jarptica [38.1K]

Answer:

r = 105

Step-by-step explanation:

Given quadratic equation:

x² − 9x − 6

Quadratic formula is given by:

(-b ± √b² - 4ac) ÷ 2a

For the equation: x² - 9x - 6

a = 1, b = -9 and c = -6

Substitute in the quadratic formula:

(-b ± √b² - 4ac) ÷ 2a

(-(-9) ± √(-9)² - 4(1*-6)) ÷ 2*1

= 9 ± √105 / 2

The solution of x² − 9x − 6 is expressed as 9 plus or minus the square root of r, all over 2

Therefore, the value of r is 105

4 0
3 years ago
−9x+y= \,\,71 71 -x-y= −x−y= \,\,-1 −1 \mathbf{Add}\text{ to eliminate }\mathbf{y.}Add to eliminate y. \mathbf{Subtract}\text{ t
Rama09 [41]

Answer:

<h3>Add to eliminate y.</h3>

Step-by-step explanation:

Given the equations

-9x + y =  71.... 1

-x - y = -1 .... 2

Using elimination method we can eliminate y first since they have the same coefficient.

To do that we will need to add up both equations. We are adding because the coefficient of y in both equations has different signs. If they have the same sign, we would have subtracted.

<em>Hence the correct option in this case is to add to eliminate y.</em>

8 0
2 years ago
A car completes a journey in 10 minutes. For the first half of the distance the speed was 60km/h and for the second half the spe
spin [16.1K]
100km long thats how long the journey was
4 0
3 years ago
Can anyone explain how to do any of this?
pashok25 [27]

Answer:

qn 10. 15mn² - 23m²n +4m³

Step-by-step explanation:

1. distribute 4m through the parenthesis

8mn² - 12m²n + 4m³ - 2n(5m² - 3nm) + nm(n-m)

2. use the commutative property to reorder the terms

8mn² - 12m²n + 4m³ - 2n(5m² - 3mn) + mn(n - m)

3. distribute -2n through the remaining parenthesis

8mn² - 12m²n + 4m³ -10m²n + 6mn² + mn² - m²n

4. collect like terms

8mn² + 6mn² + mn² - 12m²n - 10m²n - m²n + 4m³

5. complete bodmas

15mn² - 23m²n +4m³

that's is how you do it so the answer is

15mn² -23m²n + 4m³

5 0
3 years ago
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