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Electrons are spread around the atom, in layers outside of the nucleus (which holds the protons and the neutrons). These layers are called shells. The innermost shell can only hold 2 electrons, the other ...

An alkane is a chain of carbons connected together by single bonds (-C-C-C-C-C-). All carbons have to have 4 bonds, so the carbons in the middle of the chain are attached to two other carbons, and two oth...

The method we shall use is substitution. We shall replace y each term by 'x + 1' so we are able to obtain an equation in one variable. x^2 + (x+1)^2 + 18x + 20(x+1) + 81 = 0. We now expand the brackets. x...

Multiply through by both denominators, giving us the equation (2x + 3)(2x + 1) - (2x - 8)(x - 4) = (x-4)(2x +1). If we expand the brackets, we arrive at 4x^2 + 8x + 3 - (2x^2 -16x + 32) = 2x^2 -7x -4. If ...

Here we have a pair of simultaneous equations with two unknowns. There are two methods of going about this question: substitution or elimination. Today, we shall be focusing on the latter. We need a pair...