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Ed has 4 cards. There is a number on each card. Three of the numbers are 12, 6 and 15. The mean of the numbers is 10. What is the fourth number?

To find the mean you add all the numbers together and divide by the number of numbers. Call the fourth number x. Then we know that (12+6+15+x)/4 =10. then multiply both sides by 4 to get 12+6+15+x=40 which i...
SP
Answered by Sarah P. • Maths tutor
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Integrate x/((1-x^2)^0.5) with respect to x

x = sin(u), dx/du = cos(u), dx = cos(u) * du,[x/(1-x^2)^0.5)] * dx = [sin(u)/((1-(sin(u)^2))^0.5] * cos(u) * du = [sin(u)/(cos(u)^2)^0.5] * cos(u) * du = sin(u) * duIntegral of sin(u) * du = -cos(u) = -(1-si...
AP
Answered by Andrew P. • Maths tutor
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Express 5/[(x-1)(3x+2)] as partial fractions.

5 = a(3x+2) + b(x-1), x = 1, 5 = a(3+2) +b (1-1), 5 = a(5) + b(0), 5 = 5a, a = 1, x = -2/3, 5 = a(-2+2) + b(-(2/3)-1), 5 = a(0) + b(-5/3), 5 = -5b/3, b = -3, Therefore: 5/[(x-1)(3x+2)] = 1/(x-1) -3/(3x+2)
AP
Answered by Andrew P. • Maths tutor
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Differentiate sin(x)cos(x) with respect to x?

You will have to use the Product Rule. The Product rule: when y=f(x)g(x), then dy/dx=f'(x)g(x)+f(x)g'(x). In this example, f(x)=sin(x) and g(x)=cos(x). Hence f'(x)=cos(x) and g'(x)=-sin(x). Using these and s...
MM
Answered by Matthew M. • Maths tutor
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Factorise fully 6xyz + 24x^2yz + 18xy^3z^2

So we need to find common factors for each term: 6xyz, 24x 2 yz and 18xy 3 z 2 . Let's start with the numbers. Do the numbers 6, 24 and 18 have a common factor? Yes, 6 . If we take 6 out of the term we get: ...
TL
Answered by Tom L. • Maths tutor
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