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2 years ago

Solve for x. x^2+4x-21=0 A. -3, -7 B. -3, 7 C. 3, -7 D. 3, 7

Mathematics

1 answer:

Free_Kalibri [48]2 years ago

8 0

Answer:

x = 3 and x = -7

Step-by-step explanation:

The method I used is the x method, where you place the constant on the top and the coefficient of the second term on the bottom. From there, you find two numbers that multiply to get the top number (21) and add to give the bottom number (4).

You should get -3 and 7. You should be able to rewrite the equation as so:

(x - 3) (x + 7)

Set both equal to zero separately and solve:

x - 3 = 0

x = -3

x + 7 = 0

x = -7

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Wesley and brian have a total of 87 baseball cards. Wesley have 30 less than twice as many cards as brian. How many baseball car

d1i1m1o1n [39]

Brian has 39 cards and Wesley has 48 cards

Step-by-step explanation:

Let w be the number of cards Wesley has

and

b be the number of cards Brian has

Then

$w+b = 87\ \ \ \ Eqn\ 1\\w = 2b-30\ \ \ Eqn\ 2$

Putting w = 2b-30 in equation 1

$2b-30+b = 87\\3b = 87+30\\3b = 117$

Dividing both sides by 3

$\frac{3b}{3} = \frac{117}{3}\\b = 39$

Putting b=39 in equation 2

$w = 2(39)-30\\w = 78-30\\w = 48$

Hence,

Brian has 39 cards and Wesley has 48 cards

Keywords: Linear equations, variables

Learn more about linear equations at:

#LearnwithBrainly

6 0

2 years ago

Greatest common factor of 88 and 48

kupik [55]

GFC is 8. Use a tree of 88 and 48. 88= 2^3 x 11 or 2 x 2 x 2 x 11

48=2^4 x 3 or 2 x 2 x 2 x 2 x 3 see how many groups count as the number once and multiply and bam GFC. Hope I helped! (:

4 0

2 years ago

Dave drives to work each morning at about the same time. his commute time is normally distributed with a mean of 45 minutes and

Paladinen [302]

The normal distribution curve is shown in the diagram below

The percentage of time that his commute time exceeds 61 minutes is equal to the area under the standard normal curve that lies to the RIGHT of X=61

Standardising X=61 to find z-score
 $z= \frac{61-45}{5} =3.2$

from the z-table
 $P(Z\ \textgreater \ 3.2) = 1 - P(Z\ \textless \ 3.2) = 1 - 0.9993 = 0.0007 = 0.07%$

8 0

2 years ago

In professional basketball games during 2009-2010, when Kobe Bryant of the Los Angeles Lakers shot a pair of free throws, 8 time

ziro4ka [17]

Answer:

Is plausible that the successive throws are independent

Step-by-step explanation:

1) Table with info given

The observed values are given by the following table

__________________________________________________

First shot Made Second shot missed Total

__________________________________________________

Made 152 33 185

Missed 37 8 45

__________________________________________________

Total 189 41 230

2) Calculations and test

We are interested on check independence and for this we need to conduct a chi square test, the next step would be find the expected value:

Null hypothesis: Independence between two successive free throws

Alternative hypothesis: No Independence between two successive free throws

_____________________________________________________

First shot Made Second shot missed

_____________________________________________________

Made 189(185)/230=152.0217 41(185)/230=32.9783

Missed 189(45)/230=36.9783 41(45)/230=8.0217

_____________________________________________________

On this case all the expected values are higher than 5 and the sample size 230 is enough to apply the chi squared test.

3) Calculate the chi square statistic

The statistic for this case is given by:

$\chi_{cal}^2 =\sum \frac{(O_i -E_i)}{E_i}$

Where O represent the observed values and E the expected values. Replacing the values that we got we have this

$\chi_{cal}^2 =\frac{(152-152.0217)^2}{152.0217}+\frac{(33-32.9783)^2}{32.9783}+\frac{(37-36.9783)^2}{36.9783}+\frac{(8-8.0217)^2}{8.0217}=0.000003098+0.00001428+0.00001273+0.0.00005870=0.00008881$

Now with the calculated value we can find the degrees of freedom

$df=(r-1)(c-1)=(2-1)(2-1)=1$ on this case r means the number of rows and c the number of columns.

Now we can calculate the p value

$p_v =P(\chi^2 >0.00008881)=0.9925$

On this case the pvalue is a very large value and that indicates that we can fail to reject the null hypothesis of independence. So is plausible that the successive throws are independent.

5 0

2 years ago

Evaluate (42)(43)(8-3) 2 .

Dafna1 [17]

Answer: 18060

Step 1

1806(8−3)(2)

Step 2

(1806)(5)(2)

Step 3

(9030)(2)

6 0

2 years ago

Read 2 more answers