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Aneli [31]
3 years ago
9

Solve the system using the method of you choice: -x + 4y = 12 5x - 2y = -6

Mathematics
1 answer:
yKpoI14uk [10]3 years ago
7 0

Answer:

(0, 3)

Step-by-step explanation:

Let's first eliminate x.  To do this, multiply all three terms of the first equation by 5:  

-5x + 20y = 60

5x -    2y  = -6

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

         18y = 54, so that y = 3.

Substituting 3 for y in the first equation yields:

-x + 4(3) = 12, or -x = 0.  Thus, x = 0, and the solution is

(0, 3)

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I'm having trouble with #2. I've got it down to the part where it would be the integral of 5cos^3(pheta)/sin(pheta). I'm not sur
Butoxors [25]
\displaystyle\int\frac{\sqrt{25-x^2}}x\,\mathrm dx

Setting x=5\sin\theta, you have \mathrm dx=5\cos\theta\,\mathrm d\theta. Then the integral becomes

\displaystyle\int\frac{\sqrt{25-(5\sin\theta)^2}}{5\sin\theta}5\cos\theta\,\mathrm d\theta
\displaystyle\int\sqrt{25-25\sin^2\theta}\dfrac{\cos\theta}{\sin\theta}\,\mathrm d\theta
\displaystyle5\int\sqrt{1-\sin^2\theta}\dfrac{\cos\theta}{\sin\theta}\,\mathrm d\theta
\displaystyle5\int\sqrt{\cos^2\theta}\dfrac{\cos\theta}{\sin\theta}\,\mathrm d\theta

Now, \sqrt{x^2}=|x| in general. But since we want our substitution x=5\sin\theta to be invertible, we are tacitly assuming that we're working over a restricted domain. In particular, this means \theta=\sin^{-1}\dfrac x5, which implies that \left|\dfrac x5\right|\le1, or equivalently that |\theta|\le\dfrac\pi2. Over this domain, \cos\theta\ge0, so \sqrt{\cos^2\theta}=|\cos\theta|=\cos\theta.

Long story short, this allows us to go from

\displaystyle5\int\sqrt{\cos^2\theta}\dfrac{\cos\theta}{\sin\theta}\,\mathrm d\theta

to

\displaystyle5\int\cos\theta\dfrac{\cos\theta}{\sin\theta}\,\mathrm d\theta
\displaystyle5\int\dfrac{\cos^2\theta}{\sin\theta}\,\mathrm d\theta

Computing the remaining integral isn't difficult. Expand the numerator with the Pythagorean identity to get

\dfrac{\cos^2\theta}{\sin\theta}=\dfrac{1-\sin^2\theta}{\sin\theta}=\csc\theta-\sin\theta

Then integrate term-by-term to get

\displaystyle5\left(\int\csc\theta\,\mathrm d\theta-\int\sin\theta\,\mathrm d\theta\right)
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Now undo the substitution to get the antiderivative back in terms of x.

=-5\ln\left|\csc\left(\sin^{-1}\dfrac x5\right)+\cot\left(\sin^{-1}\dfrac x5\right)\right|+\cos\left(\sin^{-1}\dfrac x5\right)+C

and using basic trigonometric properties (e.g. Pythagorean theorem) this reduces to

=-5\ln\left|\dfrac{5+\sqrt{25-x^2}}x\right|+\sqrt{25-x^2}+C
4 0
3 years ago
Read 2 more answers
1/4 of 24 on tape diagram
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Draw the tape diagram: a long rectangle and divide it into 4 squares in a row.The whole rectangle represents 24 (as a whole number), you're dividing it into 4 parts because you want to know what is 1/4 of it.Now, to find the value of each square: 24:4 = 6.Put the number 6 in each square, and you have found your result.1/4 of 24 is 6.

8 0
3 years ago
7. In 2015 a club has 250 members who each
Evgen [1.6K]

2015:

250 members

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2016

250 members + 4%

$95 annual subscription + 6%

Work:

250 x 1.04 = 260

95 x 1.06 =  100.7

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Thus, the club makes $26,182 from 260 members who pay a subscription of $100.7

3 0
3 years ago
I will give brainlest answer
KonstantinChe [14]
4 units right and 4 units down
4 0
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Hunter-Best [27]
Y = -3x + 4 = Slope-intercept form
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