Member: reinout-g

Stu:
Hi, test question here, (with numbers). I'm after the basic concept and methods of nx³-nx²+c, I figure that y=mx+c is required but not sure how to get that even when I plug in the value for x1 for example.

Hey Stu,

so if I'm correct, what you're trying to find is the tangent of a function of the following form; nx ³-nx ²+c?

First find the derivative of nx ³-nx ²+c

df/dx = 3nx ²-2nx.

Now the tangent at f(x*,y*) is given by y = (df/dx*)x + c, where (x*,y*) is the point where you need to calculate the tangent

Then, to find c, we solve y* = (df/dx*)x* + c.

To give an idea look at the following example.

suppose we want to calculate the tangent of f(x) for x=1

then y = 4*1 ³-2*1 ²+6 = 8

df/dx = 12x ²-4x

so df/dx* = 12*1 ²-4*1 = 8

the tangent must then be given by y = 8x + c

fill in the point (x*,y*) = (1, 8) => 8 = 8*1 + c => c = 0

hence the tangent at (1,8) is given by y = 8x

reinout-gApr 3, 2014

+2353

jfgjj7kfkg:
what numbers multiply to get negative 112 but add to get positive 24

28 and -4,

You can derive this from the following two equations;

xy = -112
x + y = 24

the second equation gives x = 24-y.

Filling x = 24-y in in the first equation gives;

x(24-y) = -112 which can we rewritten to the quadratic expression

x ²+24x-112 = 0

Then by applying the quadratic formula we get;

Knipsel18.PNG

Knipsel19.PNG

Reinout

reinout-gApr 3, 2014

+2353

samgelinas:
qwerty:
how can i calculate the surface of the sun?

use this formula.

area=4pi*r^2

to add to that,
the radius of the sun is approximately 695,500 kilometres.

reinout-gApr 2, 2014

+2353

shelby_lynn_:
Anthony is driving at a constant speed of 47.5 miles per hour. About how many hours will it take him to drive 247 miles?

Anthony drives 47.5 miles in 1 hour,

so he drives 1 mile in 1/47.5 hour.

Then we can calculate that 247 miles takes 247/47.5 hours.

247/47.5 = 5.2 hours.

Reinout

reinout-gApr 2, 2014

+2353

KISHAUN123:
3X+Y>6

Hey Kishaun.

Your answer does not have one specific answer.

I can rewrite it to y > 6 - 3x.

If we look at all the values for which y = 6-3x we would have all the points on this line;

Knipsel17.PNG

so for y > 6-3x all the points above the line y = 6 - 3x are correct.

If you want to know more about how you rewrite inequalities, look at this page.
It might be helpful.

http://www.mathsisfun.com/algebra/inequality-solving.html

Reinout

reinout-gApr 2, 2014

+2353

quinton iversen:
a softball is thrown with 150 joules of energy. if the ball is moving at 30.0m/s,what is the mass of the ball in kg

I believe the formula you should use is E _k = (1/2)* mass * (velocity) ² {where E _k is kinetic energy}

rewriting this gives; mass = 2*E _k/(velocity) ²

2*150/(30^2)

So the answer would be 333 grams.

Reinout

reinout-gApr 2, 2014

+2353

samgelinas:
I've just discover this game...

The goal is to add identic number to have the number 2048.

Try it!!

http://gabrielecirulli.github.io/2048/

IF YOU GOT IT, TAKE A PRINT SCREEN!!

Almost had it

Knipsel15.PNG

reinout-gApr 2, 2014

+2353