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For rectangles of area 100 m^2 what is the perimeter of the rectangle with the smallest perimeter?

100=ab P=2a+2b P=2a+200/a dP/da=2-200/a^2 dP/da=0 implies 2=200/a^2 a^2=100 a=-10,10 a is a length so take positive a, a=10 so b=10 gives perimeter 40m Notice a=10 b=10 is a square Squares are rectangles of ...
DN
Answered by Daniel N. • Maths tutor
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What can I do to revise maths?

Do every past paper you can find!
AL
Answered by Anabel L. • Maths tutor
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If f(x)=8x-3, what is the inverse function?

To obtain the inverse fucntion basically all we have to do is re-arrange the equation and the do a small trick of swaping x and f(x), which can be done either at the start or at the end. Assuming we leavce i...
TA
Answered by Teresa A. • Maths tutor
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Find the integral of 3x^2 + 4x + 9 with respect to x.

We must first remember that to integrate, we must increase the power by 1 and divide by this new power. Therefore, to integrate 3x^2 + 4x + 9, we take the first term, 3x^2 . Using the above method, we find t...
DJ
Answered by Dylan J. • Maths tutor
10322 Views

Factorise and solve x^2 + 3x - 4 = 0

To factorise this equation, we must find two numbers that add together to make 3 and multiply to make -4 . These numbers must be -3 and -1 . We would then rewrite the equation as (x-3)(x-1)=0. To solve this ...
DJ
Answered by Dylan J. • Maths tutor
12264 Views