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Maths
A Level

Solve the inequality x(x+2)>8 for x.

x(x+2)>8 if and only if x^2+2x-8>0 if and only if (x+4)(x-2)>0. There are three cases: x<-4, -4 In the first case x+4<0 and x-2<0, so their product is positive: (x+4)(x-2)>0. Next x+4...

Answered by Joshua T. Maths tutor
3506 Views

The quadratic equation 2x^2+8x+1=0 has roots a and b. Write down the value of a+b and ab and a^2+b^2.

Since the quadratic has roots a and b, this means it can be fatored as 2(x-a)(x-b)=0. Expanding this out we get 2x^2-2(a+b)x+2ab=0 and matching the coefficients for the terms x^1 and x^0 we get a+b=-4 and...

Answered by Joshua T. Maths tutor
4495 Views

Why is the derivative of 2^x not x*2^(x-1)?

That technique for calculating derivatives only works for polynomial terms, that is terms of the form x^n, where n is some number. Here though our variable x is in the exponent, and so th...

Answered by Josh G. Maths tutor
3046 Views

Given that y = (( 4x + 1 )^3)sin(2x), find dy/dx.

This is an example of the chain rule.

The chain rule is the following: if y = uv, then dy/dx = udv/dx + vdu/dx

So in this case, u = ( 4x + 1)^3, v = sin(2x)

du/dx = (3)(4)( 4x + 1 )^2...

Answered by Danielle S. Maths tutor
4828 Views

Find ∫ x^2(ln(4x))dx

 ∫xln(4x)dx

Firstly , identify this question as integration by parts. Therefore set one half as value 'u' and one as value 'dv'.

Here we will set u = ln(4x).

Therefore: d...

Answered by Sally F. Maths tutor
10239 Views

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