Tuesday, November 20, 2012

Derivative of Quadratic Functions

Introduction to derivative of quadratic functions:

In calculus the derivative is a measure of how a function changes as its input changes. The derivative of a function at a chosen input value describes the best linear approximation of the function near that input value. A quadratic equation is a polynomial equation of the second degree. The general form is ax2 + bx + c . The constants a, b, and c, are called respectively, the quadratic coefficient, the linear coefficient and the constant term or free term.

Source Wikipedia.

Derivative Formulas:

1.  ` d / dx` (x n ) = n xn-1

2.  ` d/dx` (ex)  = ex

3.  ` d/dx` `(uv)` = `u(dv)/(dx)` + `v(du)/(dx)`
4. .`d/dx` `(u/v)` = `(v(du)/(dx) - u(dv)/(dx))/ v^2`

5.  `d/dx` (sin x) = cos x

6.  `d/dx ` (cos x) = -sin x

7.  `d/dx` (tan x) = sec2x

Derivatives of Quadratic Function Problems:

Derivatives of quadratic function problem 1:

Find the derivative of quadratic function (2x3 - 3x4 + x2) with respect to x.

Solution:

Given Quadratic function is  (2x3 - 3x4 + x2)

` d/dx` (2x3 - 3x4 + x2)  = `d/dx` (2x3) - ` d/dx` (3x4) + ` d/dx ` (x2) .

=  `d/dx` (2x3) - `d/dx` (3x4)  + `d/dx` (x2).

= (2 × 3) x(3-1) - (3 × 4) x(4-1) - 2x(2-1)

= 6 x2 - 12 x3 + 2 x

`d/dx` (2x3 - 3x4 + x2) =  6 x2 - 12 x3 + 2 x

Answer: The derivative of given quadratic function is  `d/dx` (2x3 - 3x4 + x2) =  6x2 - 12 x3 + 2 x

Derivatives of quadratic function problem 2:

Find the derivative of quadratic function  y = 3t2 + t3 - 30t. with respect to 't'.Is this topic free algebra help hard for you? Watch out for my coming posts.

Solution:

Given Quadratic function is y = 3t2 + t3 - 30t.

dy  = (3 × 2)t(2 - 1) dt + (1 × 3)t(3 - 1) dt - 30t(1 - 1) dt.

= 6t dt + 3t2 dt - 30dt.

= (6t + 3t2 - 30) dt

`dy/(dt)` = (6t + 3t2 - 30)

Answer:  The derivative of given quadratic function is   `d/dt` (3 t2 + t3 - 30t) =  3t2 + 6t - 30.

Derivatives of quadratic function problem 3:

Determine the second derivative of given quadratic function f(x) = 15x2 + 10x + 5 with respect to x.

Solution:

Given quadratic function is, f(x) = 15x2 + 10x + 5

The First derivative of quadratic function is f'

f' =` (df )/ (dx)`  = (15 × 2)x(2 - 1) + (10 × 1)x (1-1)

= 30x + 10

The Second derivative of quadratic function is, f''

` d^2/dx` f(x) = `d^2/dx` ( 15x2 + 10x + 5)

= `d/dx` (f')

= `d/dx` ( 30x + 10)

= ` d/dx` (30x) +` d/dx` (10)

= 30 `d/dx` (x) + `d/dx` (10)

= 30 + 0

= 30

Answer: The Second derivative of given quadratic function is 30

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