SOLUTION: I have tried these problems on completing the square and I really do not get them. The instructions say this only: Complete the square. Do not solve for x {{{x^2 +10x + __}}

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: I have tried these problems on completing the square and I really do not get them. The instructions say this only: Complete the square. Do not solve for x {{{x^2 +10x + __}}      Log On


   



Question 83144: I have tried these problems on completing the square and I really do not get them. The instructions say this only:
Complete the square. Do not solve for x
x%5E2+%2B10x+%2B+__ and


x%5E2+-3x+%2B+__


thank you!

Found 2 solutions by Mona27, ankor@dixie-net.com:
Answer by Mona27(45) About Me  (Show Source):
You can put this solution on YOUR website!
To change a normal quadratic into the completed square form, first take half the coefficient of x (10) and place it in a bracket like this:
%28x%2B5%29%5E2
Expanding this expression gives:
x%5E2%2B10x%2B25
Since we don't need the last term, we eliminate it by subtraction:
%28x%2B5%29%5E2-25
and finally you add whatever that last term (a) is:
%28x%2B5%29%5E2-25%2Ba
This method applies to the second example even if the coefficient of x is not divisible by 2:
%28x%2B3%2F2%29%5E2-9%2F4%2Bb

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
Replaced the "?" with "__" to clear the syntax error
:
They want you to find the 3rd term, which will make it a perfect square:
:
To do this, take the coefficient of x (which is 10), take half of that (5) and
square it, gives us 25
x%5E2+%2B10x+%2B+__
The third term is 25
x%5E2+%2B10x+%2B+25
Check: (x+5)^2; if you FOIL (x+5)(x+5) you get x%5E2+%2B10x+%2B+25
:
x%5E2+-3x+%2B+___
Follow the procedure as stated on the 1st problem:
half of -3 = -1.5; (-1.5)^2 =
x%5E2+-3x+%2B+2.25
Check: (x-1.5)^2; if you FOIL (x-1.5)(x-1.5) = x%5E2+-3x+%2B+2.25
:
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