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8.7 Assessed Exercises 4

Solutions in tutor’s pigeonhole by 17:00 on Tuesday 13th December, please. Feedback is available from the moodle website.

A4.1. For each of the following, sketch the region of integration and evaluate the double integral by calculating a repeated integral with appropriate limits:

Rx2ydxdy, R={(x,y):0x3,1y2};\int\!\!\!\int_{R}x^{2}y\,dxdy,\quad R=\{(x,y):0\leq x\leq 3,1\leq y\leq 2\}; \qquad(i)
Ssin(x-y)dxdy,  S={(x,y):0xπ/2,0yπ/3};\int\!\!\!\int_{S}\sin(x-y)\,dxdy,\qquad S=\{(x,y):0\leq x\leq\pi/2,0\leq y% \leq\pi/3\}; \qquad(ii)

where RR and SS are rectangles.

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A4.2. Find the general solutions to the following differential equations:

a) d2ydx2-7dydx+12y=0\frac{d^{2}y}{dx^{2}}-7\frac{dy}{dx}+12y=0.

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b) dydx-yx=1x2\frac{dy}{dx}-\frac{y}{x}=\frac{1}{x^{2}}.

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A4.3. Solve the initial value problem: dydx=x2-1y2\frac{dy}{dx}=\frac{x^{2}-1}{y^{2}}, y(0)=1y(0)=1.

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