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Solve the Following Question.(5 Marks)

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21 questions · self-marked practice — reveal the answer and mark yourself.

Question 15 Marks
Show that the general solution of defferential equation $\frac{d y}{d x}+\frac{y^2+y+1}{x^2+x+1}=0$ is given by $( x +$

y + 1) = c(1 – x – y – 2xy).

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Question 25 Marks
Find the particular solution of the following differential equations:

$2 e^{\frac{x}{y}} d x+\left(y-2 x e^{\frac{x}{y}}\right) d y=0$, when $y(0)=1$

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Question 35 Marks
Find the particular solution of the following differential equations:

(x + y) dy + (x – y) dx = 0; when x = 1 = y

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Question 45 Marks
Find the particular solution of the following differential equations:

$\frac{d y}{d x}-3 y \cot x =\sin 2 x$, when $y \left(\frac{\pi}{2}\right)=2$

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Question 55 Marks
Find the particular solution of the following differential equations:

$y(1+\log x)=(\log x x) \frac{d y}{d x}$, when $y(e)= e ^2$

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Question 85 Marks
Water is being poured into a vessel in the form of an inverted right circular cone of semi vertical angle $45^{\circ} \mathrm{c}$ in such a way that the rate of change of volume at any moment is proporational to the area of the curved surfaces which is wet at that moment. Initially, the vessel is full to a height of $2 \mathrm{cms}$. And after 2 seconds the height becomes $10 \mathrm{~cm}$. Show that after 3.5 seconds from that start, the height of water will be $16 \mathrm{cms}$.
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Question 95 Marks
The slope of the targent to the curve at any point is equal to $y+2 x$. Find the equation of the curve passing through the origin.
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Question 105 Marks
Radium decomposes at a rate proportional to the amount present at any time. If p percent of the amount disappears in one year, what percent of the amount of radium will be left after 2 years?
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Question 115 Marks
A body cools according to Newton’s law from 100°C to 60°C in 20 minutes. The temperature of the surroundings is 20°C. How long will it take to cool down to 30°C?
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Question 125 Marks
The rate of decay of certain substances is directly proportional to the amount present at that instant. Initially, there is 25 gm of certain substance and two hours later it is found that 9 gm are left. Find the amount left after one more hour
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Question 135 Marks
The rate of disintegration of a radioactive element at any time t is proportional to its mass at that time. Find the time during which the original mass of 1.5 gm will disintegrate into its mass of 0.5 gm.
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Question 145 Marks
If a body cools from 80°C to 50°C at room temperature of 25°C in 30 minutes, find the temperature of the body after 1 hour.
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Question 155 Marks
If the slope of the tangent to the curve at each of its point is equal to the sum of abscissa and the product of the abscissa and ordinate of the point. Also, the curve passes through the point (0, 1). Find the equation of the curve.
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Question 165 Marks
Find the equation of the curve which passes through the origin and has the slope x + 3y – 1 at any point (x, y) on it.
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