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@Darkness- not exactly sure which bit you mean at 11:00 - if you are referring to the h on the bottom x(x+h) this will only equal zero if the x value is zero. Otherwise there will be a number eg x=1 ; 1(1+0) = 1x1 = 1
At the end there when you are left with (1/(2sqrtx)), why is it that you only plug in 1/2 for x and not set the whole thing to -1? The graph of f(x)=sqrtx doesn't even have a point at (1,-1) so how are you trying to find a tangent line to a point that doesn't exist?
Apalion41 The point (1,-1) lies on the line f(x) = plus and minus sqrt(x). He has the two confused. I was puzzled, as it would have to have a negative gradient due to the shape of the graph, but he has found the wrong derivative and so the gradient is wrong. It should be plus and minus 1/2 if he had the correct line. Of course this gets us two different gradients, because f(x) = plus and minus sqrt(x) is not a function (which refers to a line with only one y value for any given x value). The point also lies on f(x) = -sqrt(x), which is a function, and only has one gradient for that point. He is just missing a minus, and has found the mirrored graph's gradient for that x value, if that makes any sense.
How to solve this sums below 1) dx/dy = xy 2) (1+cos 2¤) dx/dy = 2, at y =1 when ¤ = #/4 3) A rumour spreads through town at a rate which is proportional to the product of the number of people who have not heard it and those who heard it. Given that x is a fraction of the town who have heard the rumour after time t A) Form a differential equation x,t and a constant K B) If initially a fraction C of the population had heard the rumour, deduce that x= C/C+(1-C)e^-Kt C) Given that 15% had heard the rumour at 9:00am and another 15% by noon. Find what further fraction of the population would have heard the rumour at 3:00pm Those ones👆👆👆👆👆👆👆👆
