Higher Plus

The point (9, 12) lies on the circle x² + y² = 225. Work out the gradient of the tangent to the circle at that point.The point (9, 12) lies on the circle x^2 + y^2 = 225. Work out the gradient of the tangent to the circle at that point.

A bag holds 5 red, 6 blue and 6 green counters. Two are taken without replacement. Given neither is green, what is the probability both are red?

On a histogram, a 4-wide bar and a 12-wide bar have the same frequency density of 2.5. How many more values are in the wider class?

Expand and simplify (5 + 10)(5 - 10).Expand and simplify (5 + sqrt(10))(5 - sqrt(10)).

Solve x² + y² = 841 and y = x + 1 simultaneously.Solve x^2 + y^2 = 841 and y = x + 1 simultaneously.