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First, take the first differential: y' = 4x^2 -12x. At x=3 y'= 0 so therefore the function is at a point of inflection. Taking the second derivative: y'' = 8x -12. At x=3 y''= 12. As 12 is greater than 0,...

To differentiate this, we use the power rule and the chain rule. First we differentiate the outside part, which equals 2((x^2)+1). However, because the inside of the square is a function, we have to diff...

For x!=0, multiply the equation by x to get x^4+5x^2+1=0. Then substitute t=x^2 where t>=0. So the equation has a form t^2+5t+1. Then find the discriminant and two roots. One of the roots t2<0 doesn...

Get a line a form y=-ax/b-c/b, then substitute into a cirle equation (x-p)^2 +(y-s)^2=r^2. Get a quadratic and find whether a discriminant is equal to zero. If it is then the line is tangent to a circle. ...

You start by dividing 420 by whichever numbers you know that it is divisible by.

420 is obviously divisible by 10 so you can start with 10 x 42.

Then, you factorise 10 and 10 = 2 x...