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2 years ago

Dan is watching the birds in his backyard he watches none of them or 45% are sparrows how many birds are in his backyard

Mathematics

1 answer:

nadezda [96]2 years ago

3 0

Answer:

If 9 of the sparrows is 45% of the birds in the backyard, 9/x = 45/100.

Cross multiply to get 9 * 100 = 45x; simplified is 900 = 45x or 20.

This means that there are 20 birds in the backyard. You can check this by dividing 9/20 which equals 45%

none??' you mean nine?

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If 3x^2 + y^2 = 7 then evaluate d^2y/dx^2 when x = 1 and y = 2. Round your answer to 2 decimal places. Use the hyphen symbol, -,

S_A_V [24]

Taking $y=y(x)$ and differentiating both sides with respect to $x$ yields

$\dfrac{\mathrm d}{\mathrm dx}\bigg[3x^2+y^2\bigg]=\dfrac{\mathrm d}{\mathrm dx}\bigg[7\bigg]\implies 6x+2y\dfrac{\mathrm dy}{\mathrm dx}=0$

Solving for the first derivative, we have

$\dfrac{\mathrm dy}{\mathrm dx}=-\dfrac{3x}y$

Differentiating again gives

$\dfrac{\mathrm d}{\mathrm dx}\bigg[6x+2y\dfrac{\mathrm dy}{\mathrm dx}\bigg]=\dfrac{\mathrm d}{\mathrm dx}\bigg[0\bigg]\implies 6+2\left(\dfrac{\mathrm dy}{\mathrm dx}\right)^2+2y\dfrac{\mathrm d^2y}{\mathrm dx^2}=0$

Solving for the second derivative, we have

$\dfrac{\mathrm d^2y}{\mathrm dx^2}=-\dfrac{3+\left(\frac{\mathrm dy}{\mathrm dx}\right)^2}y=-\dfrac{3+\frac{9x^2}{y^2}}y=-\dfrac{3y^2+9x^2}{y^3}$

Now, when $x=1$ and $y=2$ , we have

$\dfrac{\mathrm d^2y}{\mathrm dx^2}\bigg|_{x=1,y=2}=-\dfrac{3\cdot2^2+9\cdot1^2}{2^3}=\dfrac{21}8\approx2.63$

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2 years ago

Find the m of

zzz [600]

Both of these problems will be solved in a similar way, but with different numbers. First, we set up an equation with the values given. Then, we solve. Lastly, we plug into the original expressions to solve for the angles.

[23] ABD = 42°, DBC = 35°

(4x - 2) + (3x + 2) = 77°

4x+ 3x + 2 - 2 = 77°

4x+ 3x= 77°

7x= 77°

x= 11°

ABD = (4x - 2) = (4(11°) - 2) = 44° - 2 = 42°

DBC = (3x + 2) = (3(11°) + 2) = 33° + 2 = 35°

[24] ABD = 62°, DBC = 78°

(4x - 8) + (4x + 8) = 140°

4x + 4x + 8 - 8 = 140°

4x + 4x = 140°

8x = 140°

x = 17.5°

ABD = (4x - 8) = (4(17.5°) - 8) = 70° - 8° = 62°

DBC =(4x + 8) = (4(17.5°) + 8) = 70° + 8° = 78°

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11 months ago

What is the value of -3 + 4.5 - (- 1.2)

kari74 [83]

The answer to your question is 13.5

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2 years ago

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saul85 [17]

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2 years ago

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Find x. Round to the nearest degree.

jeka94

The Law of Cosines features the 3 side lengths of a triangle, plus the measure of the angle opposite one of those sides.

We want angle x, which is opposite the side of length 39.

Then: a^2 = b^2 - 2ab cos C becomes 39^2 = 36^2 + 59^2 - 2(36)(59)cos x

or 1521 = 3481 + 1296 - 2(36)(59) cos x

Subtract (3481+1296) from both sides: 1521 - 4777 = -4248cos x

-3256 = -4248cos x

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