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3 years ago

What is the product of (x+9)(x-9)

Mathematics

2 answers:

Verdich [7]3 years ago

8 0

Answer:

x^2 - 81

Step-by-step explanation:

There is a formula called the difference of squares, which is

(a+b)(a-b) = a^2 - b^2

ivolga24 [154]3 years ago

6 0

Answer: 9x²-81x

Step-by-step explanation:

1. Reorder the terms like this: (9x)• (x-9)

2. Remove unnecessary Parentheses like this: 9x•(x-9)

3. Distribute 9x through the Parentheses like this:

9x would become 9x² (because I combined 9x and 9x which become 9x²)

(x-9) would become -81x (so if you need further explanation I took the (x-9) and made it -9x then multiplied it by the 9x because of distributive property.)

The solution: 9x²-81x

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alekssr [168]

Answer:

x ≤ 22

Step-by-step explanation:

≤ means less than or equal to

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melisa1 [442]

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Square

Step-by-step explanation:

From what it looks like I think it is a square

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The store is selling lemons at $0.64 each. Each lemon yields about 2 tablespoons of juice. How much will it cost to buy enough l

fomenos

$5.12
Each pie requires 1/2 a cup of lemon juice, you make 2 pies so you need a cup of lemon juice. There are 16 tbsp to a cup, each lemon has 2 tbsps of juice, so you’ll need 8 lemons. Each lemon cost $0.64
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3 years ago

Solve for x. 3x = 2/5

Elena-2011 [213]

X = 0.4/3
x = 13
if answer is wanted in decimal form.

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4 years ago

Cable Strength: A group of engineers developed a new design for a steel cable. They need to estimate the amount of weight the ca

KatRina [158]

Answer:

95% confidence interval for the mean breaking strength of the new steel cable is [763.65 lb , 772.75 lb].

Step-by-step explanation:

We are given that the engineers take a random sample of 45 cables and apply weights to each of them until they break. The mean breaking weight for the 45 cables is 768.2 lb. The standard deviation of the breaking weight for the sample is 15.1 lb.

Since, in the question it is not specified that how much confidence interval has be constructed; so we assume to be constructing of 95% confidence interval.

Firstly, the Pivotal quantity for 95% confidence interval for the population mean is given by;

P.Q. = $\frac{\bar X-\mu}{\frac{s}{\sqrt{n} } }$ ~ $t_n_-_1$

where, $\bar X$ = sample mean breaking weight = 768.2 lb

s = sample standard deviation = 15.1 lb

n = sample of cables = 45

$\mu$ = population mean breaking strength

Here for constructing 95% confidence interval we have used One-sample t test statistics as we don't know about population standard deviation.

So, 95% confidence interval for the population mean, $\mu$ is ;

P(-2.02 < $t_4_4$ < 2.02) = 0.95 {As the critical value of t at 44 degree

of freedom are -2.02 & 2.02 with P = 2.5%}

P(-2.02 < $\frac{\bar X-\mu}{\frac{s}{\sqrt{n} } }$ < 2.02) = 0.95

P( $-2.02 \times {\frac{s}{\sqrt{n} } }$ < ${\bar X-\mu}$ < $2.02 \times {\frac{s}{\sqrt{n} } }$ ) = 0.95

P( $\bar X-2.02 \times {\frac{s}{\sqrt{n} } }$ < $\mu$ < $\bar X+2.02 \times {\frac{s}{\sqrt{n} } }$ ) = 0.95

95% confidence interval for $\mu$ = [ $\bar X-2.02 \times {\frac{s}{\sqrt{n} } }$ , $\bar X+2.02 \times {\frac{s}{\sqrt{n} } }$ ]

= [ $768.2-2.02 \times {\frac{15.1}{\sqrt{45} } }$ , $768.2+2.02 \times {\frac{15.1}{\sqrt{45} } }$ ]

= [763.65 lb , 772.75 lb]

Therefore, 95% confidence interval for the mean breaking strength of the new steel cable is [763.65 lb , 772.75 lb].

3 0

3 years ago