• # Mathematics Revision Solutions

## Solutions

### M0001

Recall that factorises to .

Put both fractions over a common denominator.

Expand out all terms on the top.

Factorise the numerator.

Cancel the factor of (x+3).

### M0002

Subtract 3 from both sides and factorise.

Now sketch the graph of . This is a parabola through (-3,0) and (1,0), with a minimum at x=-1.

You are trying to find all the regions in which . These should be and .

### M0003

We let as the question suggests. Then .

Now substitute these into the differential equation,

and divide through by to get .

Now calculate the Integrating Factor:

Multiplying the whole differential equation by the IF, we get

Now we spot that the LHS of the equation is equal to .

So and hence .

Now we can multiply through by to see that .

Recalling that , we now write

Integrating, we arrive at the solution.

### M0004

Differentiate once by using the quotient rule.

Now simplify:

And differentiate again, using the quotient rule.

Note that this differentiation also requires the use of the product rule:

Finally, simplify and cancel a factor of (x-1).

### M0005

The trick here is to use multiple applications of the chain rule, very carefully.

Unparseable or potentially dangerous latex formula. Error 4: no dvi output from LaTeX. It is likely that your formula contains syntax errors or worse.
=\frac{\frac{d}{dx}\left(x+\sqrt{x^{2}+1}\right)}{x+\sqrt{x^{2} +1}
Unparseable or potentially dangerous latex formula. Error 4: no dvi output from LaTeX. It is likely that your formula contains syntax errors or worse.
=\frac{1+\frac{d}{dx}(x^2+1)^{\frac{1}{2}}}{x+\sqrt{x^{2} +1}

Now we simplify.

Both the numerator and denominator should be multiplied by .

On the denominator there is a factor of that can be taken out, leaving a common factor to be cancelled through.

### M0006

We are told that .

Applying H to both sides, we see that . Similarly, .

You are expected to spot that if H is applied an odd number of times, it is equivalent to H(y), and if it is applied an even number of times, it is equivalent to y.

Thus 80 times is y, and 81 times is H(y).

### M0007

Initially the particle has acceleration a = (6t - 10).

We can integrate to find velocity: v = 3t2 - 10t + c.

Initially the velocity is 3 ms-1, so c = 3.

Now integrating again, we calculate distance: x = t3 - 5t2 + 3t + d

The particle begins at O, so d = 0.

We need to find the distance travelled in the first 2 seconds. However, this is not as simple as substituting t = 2 into the equation for x.

If we factorise the velocity, v = (3t-1)(t-3), we find that v=0 when t= 1/3 or 3.

So having travelled a certain distance, at t= 1/3 the particle turns around and comes back.

The total distance it travels is thus the distance travelled when t = 1/3, added to the distance travelled between then and when t = 2.

Dist =

### M0008

Recall that

So we need to find some such that .

Equating coefficients:

sin(x): [1]

cos(x): [2]

[1]2+[2]2: so .

[1] / [2]: so

So we need to solve

This is easy, provided we remember not to lose any solutions.

so for any .

Thus

There are many other ways of approaching this question, and these are listed on the thread linked below.

### M0009

This is an exact first order differential equation of the form . It should be solved using the Integrating Factor method.

IF:

Multiply both sides of the differential equation by the integrating factor.

Unparseable or potentially dangerous latex formula. Error 4: no dvi output from LaTeX. It is likely that your formula contains syntax errors or worse.
\frac{d}{dx}\left(\frac{y}{(\tan^2\frac{x}{2})}\right) = \frac{1}{{\tan\frac{x}{2}}

Now integrate both sides, and simplify:

### M0010

Foci coordinates is (ae,0)

Therefore (rt3,0) is the foci.

Okay so Q is the intersection of the line SP and the line perpendicular to the tangent at P.

Equation of SP

Passes through (rt3,0)

Equation of line perpendicular to the tangent at P.

The gradient of any tangent to an ellipse is

Therefore

So the perpendicular gradient is [tex]\large \frac{2\sqrt3sin\theta}{3cos\theta} </tex>

Passes through (0,0)

Therefore

Okay so Q is the intersection of these two equations

First part of the parametric equation.

Rearrange to get x on its own.

Sub this into

Unparseable or potentially dangerous latex formula. Error 4: no dvi output from LaTeX. It is likely that your formula contains syntax errors or worse.
y = -\frac{\frac{3sin\theta}{2cos\theta-1}}{1-\frac{3cos\theta}{2(2cos\theta-1)}

So!

Finally Locus of Q

Okay if the parametric equation gives us a circle,

The diameter is going to cross the x axis twice and therefore when y = 0

so

At these point

Therefore diameter is and therefore radius is

Therefore

Its a circle shifted root 3 to the left.

Now to test that the parametric equation does satisfy this cartesian equation. We sub the values in.

therefore

Subbing x and y into the cartesian equation.

This means that it can be clearly seen that

Thus, the parametric equation

Does satisfy the equation and therefore must represent a circle. This means that the locus of Q must be a circle.

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