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Darya [45]
3 years ago
13

One question is all I need help on.

Mathematics
1 answer:
natka813 [3]3 years ago
5 0
Hello,

y=x²+2x
y=3x+20

==>x²+2x=3x+20
==>x²+2x-3x-20=0
==>x²-x-20=0
==>x²-2*1/2*x+1/4-20-1/4=0
==>(x-1/2)²-81/4=0
==>(x-1/2-9/2)(x-1/2+9/2)=0
==>(x-5)(x+4)=0
==>(x=5 and y= 35 ) or (x=-4 and y=-8)


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Find the exact value of the expression.<br> tan( sin−1 (2/3)− cos−1(1/7))
Sonja [21]

Answer:

\tan(a-b)=\frac{2\sqrt{5}-20\sqrt{3}}{5+8\sqrt{15}}

Step-by-step explanation:

I'm going to use the following identity to help with the difference inside the tangent function there:

\tan(a-b)=\frac{\tan(a)-\tan(b)}{1+\tan(a)\tan(b)}

Let a=\sin^{-1}(\frac{2}{3}).

With some restriction on a this means:

\sin(a)=\frac{2}{3}

We need to find \tan(a).

\sin^2(a)+\cos^2(a)=1 is a Pythagorean Identity I will use to find the cosine value and then I will use that the tangent function is the ratio of sine to cosine.

(\frac{2}{3})^2+\cos^2(a)=1

\frac{4}{9}+\cos^2(a)=1

Subtract 4/9 on both sides:

\cos^2(a)=\frac{5}{9}

Take the square root of both sides:

\cos(a)=\pm \sqrt{\frac{5}{9}}

\cos(a)=\pm \frac{\sqrt{5}}{3}

The cosine value is positive because a is a number between -\frac{\pi}{2} and \frac{\pi}{2} because that is the restriction on sine inverse.

So we have \cos(a)=\frac{\sqrt{5}}{3}.

This means that \tan(a)=\frac{\frac{2}{3}}{\frac{\sqrt{5}}{3}}.

Multiplying numerator and denominator by 3 gives us:

\tan(a)=\frac{2}{\sqrt{5}}

Rationalizing the denominator by multiplying top and bottom by square root of 5 gives us:

\tan(a)=\frac{2\sqrt{5}}{5}

Let's continue on to letting b=\cos^{-1}(\frac{1}{7}).

Let's go ahead and say what the restrictions on b are.

b is a number in between 0 and \pi.

So anyways b=\cos^{-1}(\frac{1}{7}) implies \cos(b)=\frac{1}{7}.

Let's use the Pythagorean Identity again I mentioned from before to find the sine value of b.

\cos^2(b)+\sin^2(b)=1

(\frac{1}{7})^2+\sin^2(b)=1

\frac{1}{49}+\sin^2(b)=1

Subtract 1/49 on both sides:

\sin^2(b)=\frac{48}{49}

Take the square root of both sides:

\sin(b)=\pm \sqrt{\frac{48}{49}

\sin(b)=\pm \frac{\sqrt{48}}{7}

\sin(b)=\pm \frac{\sqrt{16}\sqrt{3}}{7}

\sin(b)=\pm \frac{4\sqrt{3}}{7}

So since b is a number between 0 and \pi, then sine of this value is positive.

This implies:

\sin(b)=\frac{4\sqrt{3}}{7}

So \tan(b)=\frac{\sin(b)}{\cos(b)}=\frac{\frac{4\sqrt{3}}{7}}{\frac{1}{7}}.

Multiplying both top and bottom by 7 gives:

\frac{4\sqrt{3}}{1}= 4\sqrt{3}.

Let's put everything back into the first mentioned identity.

\tan(a-b)=\frac{\tan(a)-\tan(b)}{1+\tan(a)\tan(b)}

\tan(a-b)=\frac{\frac{2\sqrt{5}}{5}-4\sqrt{3}}{1+\frac{2\sqrt{5}}{5}\cdot 4\sqrt{3}}

Let's clear the mini-fractions by multiply top and bottom by the least common multiple of the denominators of these mini-fractions. That is, we are multiplying top and bottom by 5:

\tan(a-b)=\frac{2 \sqrt{5}-20\sqrt{3}}{5+2\sqrt{5}\cdot 4\sqrt{3}}

\tan(a-b)=\frac{2\sqrt{5}-20\sqrt{3}}{5+8\sqrt{15}}

4 0
3 years ago
Find the value of y.<br> Picture below
olga2289 [7]

We have trapezoid with congruent legs.

30x + 11y = 2x + 3

28x +11y = 3

Also we have

30x + 11y = 12

We got 2 equations:

30x + 11y = 12

28x +11y = 3 (*-1) -----> -28x -11y = -3

30x + 11y = 12

<u> -28x -11y = -3</u>

2x = 9

x=9/2

30x + 11y = 12 ------> 30*9/2 +11y =12 ------> 135+11y =12, ---> 11y = - 123,

y= - 123/11

6 0
3 years ago
George cut a cake into eight pieces. Explain what the unit fraction of the cake is.​
morpeh [17]

Answer:

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6 0
3 years ago
Convert 13 to fifths.<br> Write your answer as a fraction.
Zina [86]

Answer:

65/5

Step-by-step explanation:

You just need to multiply 13 by 5.

4 0
3 years ago
What is the additive inverse of 18xy?
Cloud [144]
An additive inverse is the value you can add to a given value such that the sum is "0".. 

Your answer is choice A
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6 0
3 years ago
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