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Prove that 8 times any triangle number is always 1 less than a square number

A triangle number is a number such that it is the sum of n consecutive integers, starting from 0. Eg 1, 1+2, 1+2+3... are the first 3 triangle numbers. The formula for the nth triangle number is well-know...

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Co-ordinate Geometry A-level: The equation of a circle is x^2+y^2+6x-2y-10=0, find the centre and radius of the circle, the co-ordinates of point(s) where y=2x-3 meets the circle and hence state what we can deduce about the relationship between them.

We have that x2 + y2 + 6x - 2y - 10 = (x+3)2 + (y-1)2 - 20 = 0 (step was motivated by the equation of a general circle (x-a)2 + (y-b)2 = ...

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A different pattern is made using 20 straight lines and 16 arcs. The straight lines and arcs are made of metal. 20 straight lines cost £12 and the cost of one straight line: cost of one arc = 2:3. Work out the total cost of metal in the pattern.

First we need to find the cost of one arc from the information we already have about the arc (20 straight lines cost £12). To do this divide the £12 total cost by the number of lines 20.12 ÷ 20 = £0.60 ea...

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(x+6) and (x+5) are the length and width, respectively, of a rectangle with area 20. Calculate the width of the rectangle.

(x+6)(x+5)=20. x2 + 11x +30=20. x2+ 11x + 10 = 0. (x+10)(x+1)=0 . x=-1 and x=-10. width= -10+5=-5 (invalid solution). width =-1+5= 4. Checking through: (-1+6)*(-1+5)=20.

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Three points have coordinates A(-8, 6), B(4, 2) and C(-1, 7). The line through C perpendicular to AB intersects AB at the point P. Find the equations of the line AB and CP.

To find the equation of a line, we need; the gradient of that line and a point on that line. To find the gradient of a line, we require two points on the line which have been prov...

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