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The normal line to a curve at a particular point is the line through that point and perpendicular to the tangent. A simple trick to remembering how to find the normal gradient, n , is that the slope of any l...

Simultaneous equations - Solution by substitution As the variables (x & y) are the same in both equations , we can substitute from one equation into the other. This will give an equation with just one va...

The conditional perfect tense should be used in a "si" clause when there is no possibility for the event to happen. It must also be used with the pluperfect tense. For example: If I had known I wou...

First, write out the equations beneath each other: 4x + y = 14 6x - y = 16 Then, label the equations a and b (let's take the top one as a, and the bottom one as b) We always look to eliminate either the x te...

The quadratic formula is x = [- b ± √( b 2 - 4 ac )]/2 a (1) , where a,b and c are the coefficents of a quadratic in the form a x^2+ b x+ c =0 (2) . To prove that this works we need to start from equation (2...