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3 years ago

Solve the system of equations -12x-5y=40 12x-11y=80

Mathematics

1 answer:

Gwar [14]3 years ago

4 0

Answer:

The answer is (-5/24, -7.5).

Step-by-step explanation:

There are two methods to solving a system of equations - substitution or elimination. In this example, we can use elimination since the coefficients of 'x' are opposite signs. To complete elmination, we simply add the equations together:

-12x - 5y = 40

-16y = 120

Use inverse operations to solve for 'y' by dividing both sides by -16 to get y = -7.5.

Next, plug in the value of 'y' into one of the equations and solve for 'x':

-12x - (5)(-7.5) = 40 or -12x + 37.5 = 40, now subtract 37.5 from both sides: -12x + 37.5 - 37.5 = 40 - 37.5 or -12x = 5/2. Lastly, divide both sides by -12 to solve for x, x = -5/24.

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Answer: -2

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Draw a vertical line through 4 on the x axis. This vertical line crosses the parabola at some point (which we'll call point A). Draw a horizontal line from point A to the y axis and note how it lands on y = 12. Therefore the point (4,12) is on this parabola.

Repeat the same steps as before to find that (8,4) is also on the parabola

We need to find the slope of the line through (4,12) and (8,4)

m = (y2 - y1)/(x2 - x1)

m = (4-12)/(8 - 4)

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3 years ago

Which statements about the system are true? Check all that apply. y =1/3 x – 4 3y – x = –7 The system has one solution. The syst

fredd [130]

Answer:

The true statements are:

- The system consists of parallel lines

- Both lines have the same slope

Step-by-step explanation:

* Lets talk about the solution of the linear equations

- There are three types of the solutions of the system of linear equations

# If the two lines intersect each other, then there is one solution

- The equations are ax+ by = c , dx + ey = f

# If the two lines parallel to each other, then there is no solution

- The equations are ax+ by = c , ax + by = d in its simplest form ,

where a is the coefficient of x , b is the coefficient of y and

c , d are the numerical terms

# If the two lines coincide (over each other), then there are infinite

solutions

- The equations are ax+ by = c , ax + by = c in its simplest form, where

a is the coefficient of x , b is the coefficient of y and c is the

numerical term

* Lets solve the problem

∵ The system of equation is:

y = 1/3 x - 4 ⇒ (1)

3y - x = -7 ⇒ (2)

- Lets put equation (1) in the form of equation (2)

∵ y = 1/3 x - 4 ⇒ multiply both sides by 3

∴ 3y = x - 12 ⇒ subtract x from both sides

∴ 3y - x = -12

∴ Equation (1) is 3y - x = -12

∵ Equation (2) is 3y - x = -7

∵ The coefficients of x and y in the two equation are equal

∵ The numerical terms in the two equations are not equal

∴ The equations have no solution because their lines are parallel

∵ The parallel lines have same slope

* The true statements are

- The system consists of parallel lines

- Both lines have the same slope

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3 years ago

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a math teacher claims that she has developed a review course that increases the score of students on the math portion of a colle

madam [21]

Answer:

$H_0: \mu\leq514\\\\H_1: \mu>514$

B. Z=2.255. P=0.01207.

C. Although it is not big difference, it is an improvement that has evidence. The scores are expected to be higher in average than without the review course.

D. P(z>0.94)=0.1736

Step-by-step explanation:

<em>A. state the null and alternative hypotheses.</em>

The null hypothesis states that the review course has no effect, so the scores are still the same. The alternative hypothesis states that the review course increase the score.

$H_0: \mu\leq514\\\\H_1: \mu>514$

B. test the hypothesis at the a=.10 level of confidence. is a mean math score of 520 significantly higher than 514? find the test statistic, find P-value. is the sample statistic significantly higher?

The test statistic Z can be calculated as

$Z=\frac{M-\mu}{s/\sqrt{N}} =\frac{520-514}{119/\sqrt{2000}}=\frac{6}{2.661}=2.255$

The P-value of z=2.255 is P=0.01207.

The P-value is smaller than the significance level, so the effect is significant. The null hypothesis is rejected.

Then we can conclude that the score of 520 is significantly higher than 514, in this case, specially because the big sample size.

C. do you think that a mean math score of 520 vs 514 will affect the decision of a school admissions adminstrator? in other words does the increase in the score have any practical significance?

Although it is not big difference, it is an improvement that has evidence. The scores are expected to be higher in average than without the review course.

D. test the hypothesis at the a=.10 level of confidence with n=350 students. assume that the sample mean is still 520 and the sample standard deviation is still 119. is a sample mean of 520 significantly more than 514? find test statistic, find p value, is the sample mean statisically significantly higher? what do you conclude about the impact of large samples on the p-value?

In this case, the z-value is

$Z=\frac{520-514}{s/\sqrt{n}} =\frac{6}{119/\sqrt{350}} =\frac{6}{6.36} =0.94\\\\P(z>0.94)=0.1736>\alpha$

In this case, the P-value is greater than the significance level, so there is no evidence that the review course is increasing the scores.

The sample size gives robustness to the results of the sample. A large sample is more representative of the population than a smaller sample. A little difference, as 520 from 514, but in a big sample leads to a more strong evidence of a change in the mean score.

Large samples give more extreme values of z, so P-values that are smaller and therefore tend to be smaller than the significance level.

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