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The probability that John picks out a red ball is: The number of red balls divided by the total number of balls = 4/10
Because the balls are replaced, each event is independent so every time John pic...

equation of a circle: (x - a)^2 + (y - b)^2 = r^2, where the circle has centre (a, b) and radius r.
Let's draw the diagram, where (x, y) is some point on the circle, which for ease we'll call P, and...

Use the method of substitution to answer this question.
Step 1: Rearrange one of the equations to find x or y.
y-x=3 y=x+3
Step 2: Substitute your y into the first equation
x^2<...

When we are presented with a quadratic equation in this form, and asked to expand, it is important to make sure that every term is used. For example, we would begin with the 'x' from the (x+1) bracket, an...

In terms of structure I think it's important to break down the question into manageable chunks. This can be explained in the introduction - from my experience it's usually best practice to write an introd...