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A circle with centre C has equation x^2 + y^2 + 2x + 6y - 40 = 0 . Express this equation in the form (x - a)^2 + (x - b)^2 = r^2. Find the co-ordinates of C and the radius of the circle.

We can express the equation of any circle in the form (x - a)^2 + (y- b)^2 = r^2 . The centre of the circle is then the point (a, b) and its radius is r . If we multiply out the brackets in the equation abov...
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Answered by Baran K. • Maths tutor
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The line AB has equation 3x + 5y = 7. What is the gradient of AB?

The gradient of a line in the form y = ax + b, where a and b are some numbers, is the number a . So we need to get the equation 3x + 5y = 7 into the above form, with y on one side on its own! We first move t...
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Answered by Baran K. • Maths tutor
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When should I use the perfect and imperfect tenses when talking about past actions?

For this question we will use the verb manger (to eat) as an example. The perfect tense is used to describe an action which took place once in the past. You can think of it as a single, completed action . EX...
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Answered by Laura G. • French tutor
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What does a velocity-time graph represent?

The first step in answering any question is to figure out what the question really means! Velocity is a term physicists use to describe not just speed, but speed in a particular direction. When we talk about...
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Answered by Iman S. • Physics tutor
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What does it take to make a 7 in HL Economics?

Most IB students pick HL Economics thinking it is an easy seven that can boost their total score. However, IB economics is one of the most instense courses offered by the IBO. There are five main steps to ta...
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Answered by Youssef M. • Economics tutor
28558 Views