Tuesday, November 29, 2011

Show that (2x-1)^2-(x-3)^2 can be simplified to (3x-4)(x+2)?

We'll expand the squares using the
formula:


(a+b)^2 = a^2 + 2ab +
b^2


(a-b)^2 = a^2 - 2ab +
b^2


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


(2x-1)^2 = 4x^2 - 4x + 1
(1)


(x-3)^2 = x^2 - 2*x*3 +
3^2


(x-3)^2 = x^2 - 6x + 9
(2)


We'll subtract (2) from
(1):


4x^2 - 4x + 1 -  x^2 + 6x -
9


We'll combine like
terms:


3x^2 + 2x - 8


We'll
determine the roots of the quadratic:


3x^2 + 2x - 8 =
0


x1 = [-2+sqrt(4+96)]/6


x1 =
(-2+10)/6


x1 = 8/6


x1 =
4/3


x2 = (-2-10)/6


x2 =
-2


The quadratic could be written as a product of linear
factors:


3x^2 + 2x - 8 = 3(x - 4/3)(x +
2)


We'll multiply by 3 the first
factor:


3(x - 4/3)(x + 2) = (3x - 4*3/3)(x +
2)


3x^2 + 2x - 8 =
(3x-4)(x+2)


(2x-1)^2 - (x-3)^2 = (3x-4)(x+2)
q.e.d.

No comments:

Post a Comment

How is Anne's goal of wanting "to go on living even after my death" fulfilled in Anne Frank: The Diary of a Young Girl?I didn't get how it was...

I think you are right! I don't believe that many of the Jews who were herded into the concentration camps actually understood the eno...