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3 years ago

If a+b+c=6,ab+bc+ca=11,then what is a3+b3+c3-3abc

Mathematics

2 answers:

kipiarov [429]3 years ago

7 0

(a+b+c)^3=a^3 +b^3+c^3-2(ab+ac+bc)

216=a^3+b^3+c^3-2(11)

a^3+b^3+c^3=238

but ıdk how can ı find -3abc :/

adell [148]3 years ago

6 0

<h3>Answer: 18</h3>

===============================================

Work Shown:

a+b+c = 6

(a+b+c)^2 = 6^2

(a+b+c)(a+b+c) = 36

a(a+b+c)+b(a+b+c)+c(a+b+c) = 36

a^2+ab+ca+ab+b^2+ca+bc+c^2 = 36

a^2+b^2+c^2+2ab+2bc+2ca = 36

a^2+b^2+c^2+2(ab+bc+ca) = 36

a^2+b^2+c^2+2*11 = 36

a^2+b^2+c^2+22 = 36

a^2+b^2+c^2 = 36-22

a^2+b^2+c^2 = 14

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a^3+b^3+c^3-3abc = (a+b+c)*(a^2+b^2+c^2 - (ab+bc+ca) )

a^3+b^3+c^3-3abc = 6*(14 - 11)

a^3+b^3+c^3-3abc = 18

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Kay [80]

Answer:

$\frac{(82)(2.4)^2}{104.139} \leq \sigma^2 \leq \frac{(82)(2.4)^2}{62.132}$

$4.535 \leq \sigma^2 \leq 7.602$

Now we just take square root on both sides of the interval and we got:

$2.2 \leq \sigma \leq 2.8$

And the best option would be:

A. 2.2 < σ < 2.8

Step-by-step explanation:

Information provided

$\bar X=32.1$ represent the sample mean

$\mu$ population mean

s=2.4 represent the sample standard deviation

n=83 represent the sample size

Confidence interval

The confidence interval for the population variance is given by the following formula:

$\frac{(n-1)s^2}{\chi^2_{\alpha/2}} \leq \sigma^2 \leq \frac{(n-1)s^2}{\chi^2_{1-\alpha/2}}$

The degrees of freedom are given by:

$df=n-1=83-1=82$

The Confidence is given by 0.90 or 90%, the value of $\alpha=0.1$ and $\alpha/2 =0.05$ , the critical values for this case are:

$\chi^2_{\alpha/2}=62.132$

$\chi^2_{1- \alpha/2}=104.139$

And replacing into the formula for the interval we got:

$\frac{(82)(2.4)^2}{104.139} \leq \sigma^2 \leq \frac{(82)(2.4)^2}{62.132}$

$4.535 \leq \sigma^2 \leq 7.602$

Now we just take square root on both sides of the interval and we got:

$2.2 \leq \sigma \leq 2.8$

And the best option would be:

A. 2.2 < σ < 2.8

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3 years ago

An elephant needs to drink at least 40 gallons of water each day. A drinking tank contains 4 gallons of water. The elephant has

kirill115 [55]

Answer:

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Step-by-step explanation

24+4x≥40. Subtract 24 from both sides to get 4x≥16. Divide both sides by 4 to get x≥4.

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3 years ago

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Art [367]

Answer:

y = (x + 4)²

Step-by-step explanation:

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y = x²+ 8x + 16

By using identity (a + b)² = a² + 2ab + b²

y = x² + 2(4)(x) + 4²

Here a = x and b = 4

y = (x + 4)²

Therefore, factored form of the given equation is y = (x + 4)²

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3 years ago

A sixth grade student bought three cans of tennis balls for $4 each. Sales tax for all three cans with $0.95. Write an expressio

Murrr4er [49]

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3 years ago

Are the following (correct , incorrect , linear , nonlinear ) 7n, n+(n+1)+(n+2) , 3n”2 squared “ , 2n+8, n(3 squared) div 2

Maslowich

<h3>Answers:</h3>

A) Correct. Linear.
B) Correct. Linear.
C) Incorrect. Nonlinear.
D) Incorrect. Linear.
E) Correct. Nonlinear.

=======================================================

Explanation:

The product of a number n and 7 is the same as n*7 or 7*n or 7n

The number next to the variable implies multiplication, so we don't have to write the asterisk or multiplication symbol.

This expression is linear because the exponent is 1. Think of 7n as 7n^1

Or you could graph it out and you would get a straight line.

-------------------

n = first number

n+1 = number right after number n

n+2 = number right after n+1

This shows we have 3 consecutive numbers

The sum of this leads to 3n+3 which is linear.

-------------------

Tina needs to square 3n to get (3n)^2. So she forgot to square the 3

(3n)^2 is equivalent to 9n^2

Both of which are nonlinear. They graph out a curved parabola which isn't a straight line. The exponent being larger than 1 is another indication of a nonlinear expression.

-------------------

The sum of a number and 8 can be represented by n+8 where n is the unknown number. Then sticking "twice" out front means we double all of n+8. So we double it to get 2(n+8) which is equivalent to 2n+16

Tina mistakenly only doubled the n and not the 8

2(n+8) and 2n+16 are both linear. It might help to think of it like y = 2x+16 and to graph that out to get a straight line.

-------------------

E) Tina is correct here in dividing n^3 over 2

This is nonlinear since the exponent is larger than 1. It graphs out a curved cubic, rather than a straight line.

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1 year ago