Showing posts with label Quadratics. Show all posts
Showing posts with label Quadratics. Show all posts

Sunday, May 24, 2015

Determine Algebraically whether f(x) = 1 + x + x^2 is even, odd, or neither

A function is even if f(x) = f(-x), but for our function

f(-x)=1-x+x^2

so it is not even.

To be odd -f(x)=f(-x), and for our function

-f(x) = -1-x-x^2

and so it is also not odd.

Therefore it is neither.

Wednesday, July 24, 2013

Find the quadratic equation whose roots are twice the roots of 4x^2+8x-5=0.

ax^2+bx+c
4x^2+8x-5=0 
since a*c=-20 
we use 10 and -2 as follows 

4x^2+10x-2x-5=0 
2x(2x+5)-1(2x+5)=0 
(2x-1)(2x+5)=0 
so x=1/2 or x=-5/2 
and so 
(x-1)(x+5)=0 
x^2-6x-5=0 

:)

Sunday, July 21, 2013

Derive a quadratic equation using the following points: (1, -4), (2, -5), (3, -10)

y = ax^2+bx+c 
(1) (1, -4) -> -4=a+b+c , 
(2) (2, -5) -> -5= 4a+2b+c, 
(3) (3, -10) -> -10=9a+3b+c 

(2)-(1): 
-5+4=4a-a+2b-b+c-c 
-1=3a+b (or 3a+b=-1) 
(3)-(1): 
-6=8a+2b (or 4a+b=-3) 

taking the difference of these 2 we get 

4a-3a+b-b=-3+1 (or a=-2) 

and thus b=5 
Now from (1):
-4=-2+5+c (so c=-7) 



y=-2x^2+5x+-7 

:) 

Sunday, May 12, 2013

for each of the following find: A) the vertex, B)the y intercept, C) the x intercept of f(x)=(x-1)^2-2

This parabola is in standard form - which is nice: 
%0D%0Af%28x%29=%28x-1%29%5E2-2%0D%0A 
%0D%0Af%28x%29=a%28x-h%29%5E2%2Bk%0D%0A 
%0D%0AV%28h%2Ck%29%0D%0A 


so our vertex is (1,-2) 

to get the y-intercept set x=0, then 


f%280%29=%280-1%29%5E2-2=1-2=-1 

to get the x-intercept set f(x)=0, then 

%0D%0A0=%28x-1%29%5E2-2%0D%0A 
%0D%0A2=%28x-1%29%5E2%0D%0A 


%0D%0Aabs%28x-1%29=2%0D%0A 

so that 
x-1=2 or x-1=-2
x=0 or x=-1 

x-intercepts: {0, -1} 

:)

Thursday, May 9, 2013

Tuesday, May 7, 2013

Finding Axis of symmetry


f(x) = (x − 5)2 + 2
i need a axis of symmetry

Your Answer:
If by f(x) = (x − 5)2 + 2
you mean:

f%28x%29+=+%28x+-+5%29%5E2+%2B+2

then we can use the fact that this equation is in standard form. This means that

x-5=0

gives us what we need to determine the axis of symmetry.
Therefore the axis of symmetry is:

x=5

:)

Tuesday, April 23, 2013

Factoring Quadratics expressions,


Factoring quadratics usually gives students headaches, bu it does not have to be this way. Let's go over some facts that will help us. 

  • Not every quadratic can be factored into binomials (unless you factor over the complex numbers) 
  • Factoring may be sometimes called finding the zeros, or solving for x
  • Special factoring identities are very useful - so try them first
  • There are several valid factoring methods but they all depend on finding a pair of factors of the product of the coefficients a and c and that add to the coefficient b 

I have been posting several factoring examples, look for them under the labels factoring, factoring polynomials, factoring quadratics, etc.

Thursday, April 18, 2013

Complete the square

Complete the square. Fill in the number that makes the polynomial a perfect-square quadratic.

d2 + 14d +

Solution:








So we add 49 to get a perfect square