SOLUTION: 2. When the sum of 3 and twice a positive number is subtracted from the square of the number, the result is 0. Find the number. Show clear solution thanksss!

Algebra ->  Equations -> SOLUTION: 2. When the sum of 3 and twice a positive number is subtracted from the square of the number, the result is 0. Find the number. Show clear solution thanksss!      Log On


   

Question 1172177: 2. When the sum of 3 and twice a positive number is subtracted from the square of the number, the result is 0. Find the number. Show clear solution thanksss!
Found 2 solutions by Cromlix, math_helper:
Answer by Cromlix(4381) About Me  (Show Source):
You can put this solution on YOUR website!
Hi there,
Making x the positive number
x^2 - 3 + 2x = 0
Rearrange
x^2 - (2x - 3) = 0
x^2 - 2x + 3 = 0
Factorise
(x + 1)(x - 3) = 0
x + 1 = 0
x = -1
x - 3 = 0
x = 3 (Disregard as negative)
x = 3 is the answer.
Hope this helps :-)

Answer by math_helper(2461) About Me  (Show Source):
You can put this solution on YOUR website!


Saw an error in tutor Cromlix' answer, so came in to show the fix:

The expression should be:
+x%5E2+-+%282x+%2B+3%29+=+0+, leading to...

+x%5E2+-+2x+-+3+=+0+
+%28x-3%29%28x%2B1%29+=+0+

x=3 and/or x=-1
Keeping just the positive answer, +highlight%28+x=3+%29+
--------------------------------
Tutor Cromlix tried to fix his answer, and while he arrives at the correct answer of x=3 this time, his steps still contain several errors: 


Hi there,

Making x the positive number

x^2 - 3 + 2x = 0          <<< should be  x^2 - 3 - 2x = 0

Rearrange

x^2 - (2x - 3) = 0 

x^2 - 2x + 3 = 0          

Factorise

(x + 1)(x - 3) = 0        <<< this is NOT the correct factorization of x^2-2x+3, rather is is the correct factorization of x^2-2x-3 

x + 1 = 0

x = -1

x - 3 = 0

x = 3 (Disregard as negative)    <<<  left over from before his edits (??)

x = 3 is the answer.        <<< yes, correct

Hope this helps :-)