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How can I integrate e^x sin(x)?

This integral is a particularly difficult integral that has shown up in STEP questions before. It's not hard because of how difficult the actual calculations are, but more because of how hard it is to spo...

Answered by Lawrence H. STEP tutor
2230 Views

Show that if a polynomial with integer coefficients has a rational root, then the rational root must be an integer. Hence, show that x^n-5x+7=0 has no rational roots.

Let f(x)=x^n+a_(n-1)x^(n-1)+...+a_0 with n>=2 and a_i an integer have a rational root x=p/q.

Consider q^(n-1)f(p/q).

q^(n-1)f(p/q)=p^n/q+a_(n-1)p^(n-1)+...+a_0q^(n-1)=0

==> a_(n...

Answered by Peter A. STEP tutor
5183 Views

Show that substituting y = xv, where v is a function of x, in the differential equation "xy(dy/dx) + y^2 − 2x^2 = 0" (with x is not equal to 0) leads to the differential equation "xv(dv/dx) + 2v^2 − 2 = 0"

This is the first part of a Step 1 question (2012 question 8), and is fairly typical in that it requires A Level Maths understanding to be applied in a number of different ways, out of the usual context.W...

Answered by Will W. STEP tutor
9814 Views

Prove that any number of the form pq, where p and q are prime numbers greater than 2, can be written as the difference of two squares in exactly two distinct ways.

If we want to prove it, we need to prove every odd number can be expressed as the difference of two squares, which is very easy.

Suppose this odd number to be 2n-1, then we can see 2n-1=n...

Answered by Shibo L. STEP tutor
6872 Views

Find all positive integers n such that 12n-119 and 75n-539 are both perfect squares. Let N be the sum of all possible values of n. Find N.

Let 75n - 539 = l^2 and 12n - 119 = k^2 . where n is a natural number.

Multiply 75n - 539 = l^2 by 4 to give 300n - 2156 =4l^2 and 12n - 119 = k^2 by 25 to give 300n - 2975 = 25k^2.

Subtract...

Answered by Soham K. STEP tutor
7207 Views

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