Please help explain calculus to me

Ah that's where I'm going wrong then I need a new c. Yes, of course I do and I realise why now. My x= -1 and my m=1 so does this look right? -1/1(-1) = 1. Is that my y= ?

So you found the gradient of the tangent, and then because the gradient of the normal is perpedicular, the gradient is -1/gradient of tangent.

and you know the equation of a straight line is y = mx + c

so you get the value for the gradient at the x coordinate of where the normal crosses the curve. (i.e. substituting x value into your dy/dx equation to get gradient)

then put in the value of m (-1/gradient of line), and x into the straight line equation. You also know the y coordinate of where the normal crosses the curve (or if you dont, substitute the x value into the original equation of the curve and solve), so put in that value.

you should now have an equation y = mx + c, where you only dont know 'c', so solve to find c.

Then you have the equation of the normal

Sorry basically wasnt sure exactly what you'd done so thought id write it all out for you to check against

edit: I think the -1/1(-1) is just mx. so no that is not y. y=mx+c, so you need to plug in the value of y at x=-1 and solve to find c. then you have your equation. unless iv missunderstood! - hope that helps anyway

What you say makes sense, but somehow I'm not getting anything sensible so am probably doing something really stupid.


The m is the gradient, right? So my gradient of my tangent equals m= 1 therefore the gradient of the normal is -1/1



I'm trying to find the normal at x= -1. So dy/dx= 6(-1) +7
m= 1?

y= -2
y =mx+c
-2=-1/1(-1)+c

-2 + -1/1(-1) =c
-2 -1 = -3
c= -3
y= 1x -3


Thank-you for trying to help.

Did you read what I wrote sweetie? it might help if your still stuck.

What you say makes sense, but somehow I'm not getting anything sensible so am probably doing something really stupid.


The m is the gradient, right? So my gradient of my tangent equals m= 1 therefore the gradient of the normal is -1/1



I'm trying to find the normal at x= -1. So dy/dx= 6(-1) +7
m= 1?

y= -2
y =mx+c
-2=-1/1(-1)+c

-2 + -1/1(-1) =c
-2 -1 = -3
c= -3
y= 1x -3


Thank-you for trying to help.

Everything youv done is right, except that last line. the 1 is the gradient of the tangent, the gradient of the normal is -1. so y = -x - 3

I think it might be a bit confusing using 'm' as the gradient of the tangent. because in y=mx+c for the normal, the gradient would be -1/m, not m.. if that makes sense?

if you say the gradient of the tangent is 'n' = 1

the gradient of the normal is -1/n = -1 which = the 'm' in y=mx+c

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Can't recommend this website enough!!! Just watch the video about stationary points and differentiation. The guy makes it really logical and easy to understand.