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How do I know when to use the perfective or imperfective aspect of a verb?

While the tense of a verb describes when an action takes place in time, the aspect describes how it takes place (whether it was done repeatedly or once, whether it is an ongoing process or a sudden action, e...
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Answered by Daria K. • Russian tutor
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Given that the quadratic equation x^2 + 7x + 13 = 0 has roots a and b, find the value of a+b and ab.

Remember that for a general quadratic equation Ax^2 + Bx + C = 0, the sum of the roots = -B/A and the product of the roots = C/A.In our question, A = 1, B = 7, C = 13.So a + b = -7/1 = -7 and ab = 13/1 = 13
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Differentiate y = x sin(x)

The question is asking to differentiate which means find dy/dx. If we think about the differentiation rules we know about, we see that we should use the product rule as y is a product (multiplication) of two...
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Answered by Nathan T. • Maths tutor
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Difference between Comparative advantage and Absolute advantage

A comparative advantage is when a country can produce a good at a lower opportunity cost than another country. For example, if the UK can produce 10 pharmaceuticals or 5 cars, whereas Belgium can produce 4 c...
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Answered by Conor T. • Economics tutor
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A sample of CaCO3 has been weighed in at 6.3 g. How many moles of calcium carbonate are present?

The first thing to think of here is what does a mole actually mean?Using the equation: Moles = Mass (g) / Molar Mass we can first find out what the molar mass of CaCO 3 is.TO THE PERIODIC TABLE!1) List the i...
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Answered by Thomas C. • Chemistry tutor
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