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3 years ago

Solve each equation by completing the square r² = –12r - 35

Mathematics

1 answer:

Fittoniya [83]3 years ago

7 0

Answer:

r = - 7, r = - 5

Step-by-step explanation:

Given

r² = - 12r - 35 ( add 12r to both sides )

r² + 12r = - 35

To complete the square

add ( half the coefficient of the r- term )² to both sides

r² + 2(6)r + 36 = - 35 + 36

(r + 6)² = 1 ← take the square root of both sides )

r + 6 = ± 1 ( subtract 6 from both sides )

r = - 6 ± 1, thus

r = - 6 - 1 = - 7 or r = - 6 + 1 = - 5

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The mean amount spent by a family of four on food per month is $500 with a standard deviation of $75. Assuming that the food cos

JulijaS [17]

Answer:

The probability that a family spends less than $410 per month

P( X < 410) = 0.1151

Step-by-step explanation:

Step(i):-

Given mean of the population = 500

Given standard deviation of the Population = 75

Let 'X' be the variable in normal distribution

$Z = \frac{x-mean}{S.D}$

Given X = $410

$Z = \frac{410-500}{75} = - 1.2$

Step(ii):-

The probability that a family spends less than $410 per month

P( X < 410) = P( Z < - 1.2 )

= 0.5 - A( -1.2)

= 0.5 - A(1.2)

= 0.5 - 0.3849 ( ∵from normal table)

= 0.1151

Final answer:-

The probability that a family spends less than $410 per month

P( X < 410) = 0.1151

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3 years ago

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4 years ago

In a running competition, a bronze, silver and gold medal must be given to the top three girls and top three boys. If 15 boys an

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Answer:

There are a total of possible 1820 results.

Step-by-step explanation:

Since there are two competitions, one for boys and one for girls, and we want all the possible results we will calculate the possible combinations for the boys and multiply them by the possible combinations for the girls. This is shown below:

$Boys = \frac{15!}{3!(15 - 3)!} = \frac{15!}{3!12!} = \frac{15*14*13*12!}{3!12!}\\Boys = \frac{15*14*13}{3*2*1}\\Boys = \frac{15*14*13}{3*2*1}\\Boys = 455$