Wednesday, October 6, 2010

Complete the squares x^2-14x+_ 9x^2-30x+_ 25x^2+_+36y^2 9x^4/25-_+25x^2/9 x^2+_+1/4

1) To complete the given squares, we'll have to work
according to the formula:


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


(a-b)^2 = a^2 - 2ab +
b^2


We'll analyze the first
expression


x^2-14x+_


We'll
identify a^2 = x^2 => a = x


To calculate b, we'll
consider the second term of the square:


-14x =
-2*a*b


-14x = -2*x*b


We'll use
the symmetric property and we'll divide by 2x:


b =
-7


Now, we'll complete the square by adding the amount
b^2.


b^2 = (-7)^2


b^2 =
49


(a+b)^2 = (x-7)^2


The
missing term in the quadratic expression is
49:


(x-7)^2 = x^2 - 14x +
49


2) We notice that the missing term is
b^2.


We'll identify a^2 = 9x^2 => a = sqrt 9x^2
=> a = 3x


9x^2-30x+_


To
calculate b, we'll consider the second term of the
square:


-30x = -2*a*b


-30x =
-2*3x*b


-30x = -6x*b


We'll
divide by 6x:


b = -5 => b^2 =
25


The missing term in the quadratic expression is 25 and
the completed square will be:


(3x-5)^2 =
9x^2-30x+25


3) We notice that the missing
term is 2ab.


We'll identify a^2 = 25x^2 => a = sqrt
25x^2 => a = 5x


b^2 = 36y^2 => b = sqrt 36y^2
=> b =
6y


25x^2+_+36y^2


2ab =
2*5x*6y


2ab = 60xy


The missing
term in the quadratic expression is 60xy and the completed square will
be:


(5x+6y)^2 = 25x^2 + 60xy +
36y^2


4) We notice that the missing term is
2ab.


We'll identify a^2 = 9x^4/25 => a = sqrt
9x^4/25 => a = 3x^2/5


b^2 = 25x^2/9 => b =
sqrt 25x^2/9 => b =
-5x/3


9x^4/25-_+25x^2/9


-2ab =
-2*3x^2*5x/5*3


-2ab =
-2x^3


The missing term in the quadratic expression is -2x^3
and the completed square will be:


(3x^2/5 -
5x/3)^2 = 9x^4/25- 2x^3 + 25x^2/9


5) We
notice that the missing term is 2ab.


We'll identify a^2 =
x^2 => a = sqrt x^2 => a = x


b^2 = 1/4
=> b = sqrt 1/4 => b =
1/2


x^2+_+1/4


2ab =
2x/2


2ab = x


The missing term
in the quadratic expression is x and the completed square will
be:


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

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