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The picture illustrates the sum 1 + 2 + 3 + 4 = (4 x 5)/2. Prove the general formula for the sum of the first n natural numbers and the formula for the sum of the cubes of the first n natural numbers.
Use the animation to help you work out how many lines are needed to draw mystic roses of different sizes.
Watch the video to see how Charlie works out the sum. Can you adapt his method?