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Solve the equation cos2x - 5cosx = 2

cos2x= 2cos^2x - 1 2cos^2x - 1 - 5cosx = 2 Let cosx = y 2y^2 - 5y - 3 = 0 (2y + 1)(y + 3) = 0 y = -1/2 or -3 cosx = -1/2 or -3 x = 120 degrees
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Answered by Pearl V. • Maths tutor
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Expand the expression (1+3x)^1/3 up to the term x^3.

= 1 + 3x 1/3 + (1/3 -2/3)(3x)^2 + (1/3*-2/3*-5/3)(3x)^3 = 1 + x - 2x^2 + 10x^3
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Answered by Pearl V. • Maths tutor
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Pushing a mass up a slope and energy

Please note: knowledge of the SUVAT equations, friction and trigonometry is required for this thread. Energy comes in many forms, and here we will focus on kinetic energy (KE) and potential energy (PE). Belo...
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Answered by Daniel S. • Maths tutor
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What is a Tree Diagram?

A Tree Diagram is a useful tool to calculate probabilities. By drawing a "Tree Diagram" and writing down all possible outcomes, it is very easy to calculate simple probabilities by moving through t...
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Answered by Fahmeed R. • Maths tutor
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How Would I Factorise A Quadratic Equation?

Factorising is a way of 'converting' an equation into a form with brackets in order to make it more useful and easier to manipulate. It is the reverse of expanding an equation. For example: To factorise the ...
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Answered by Cameron G. • Maths tutor
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