Factorise -2x^2-6x+9?
2008-07-11 9:05 am
I've never been good with factorising. i can expand fine, and i can do the simple ones but the 9 is killing me. why cant it be an 8?! Please help.
回答 (11)
2008-07-11 9:09 am
✔ 最佳答案
/this can't be factor
2008-07-11 8:39 pm
it cannot be factorised lah....
2008-07-11 6:45 pm
-2x^2 - 6x + 9
= cannot be factored
= cannot be factored
2008-07-11 4:59 pm
Factoring it this way might help...
-2x^2 - [ (3-3*sqrt(3)) + (3+3*sqrt(3)) ]x + 9 = 0
Then, you would do the usual...
take -2x out which will give,
-2x [ x + ((3+3*sqrt(3))/2) ] + (3 - 3*sqrt(3)) [ x + ((3+3*sqrt(3))/2) ] = 0
-2x + (3 - 3*sqrt(3)) = 0
x + ((3+3*sqrt(3))/2) = 0
The roots are,
x = - (3+3*sqrt(3))/2
x = - (3-3*sqrt(3))/2
-2x^2 - [ (3-3*sqrt(3)) + (3+3*sqrt(3)) ]x + 9 = 0
Then, you would do the usual...
take -2x out which will give,
-2x [ x + ((3+3*sqrt(3))/2) ] + (3 - 3*sqrt(3)) [ x + ((3+3*sqrt(3))/2) ] = 0
-2x + (3 - 3*sqrt(3)) = 0
x + ((3+3*sqrt(3))/2) = 0
The roots are,
x = - (3+3*sqrt(3))/2
x = - (3-3*sqrt(3))/2
2008-07-11 4:58 pm
there's no answer to this problem. it has no real roots.
2008-07-11 4:42 pm
Can`t be done I`m afraid.
2008-07-11 4:22 pm
if your question is right..
then it does not have rational roots
solve by the following method taking discriminant
a=-2
b=-6
c=9
d=b^2 - 4ac
x= (-b+d^1/2)/2a and x= (-b-d^1/2)/2a
then it does not have rational roots
solve by the following method taking discriminant
a=-2
b=-6
c=9
d=b^2 - 4ac
x= (-b+d^1/2)/2a and x= (-b-d^1/2)/2a
2008-07-11 4:18 pm
this can't be factorised, sorry
2008-07-11 4:15 pm
i just tried solving but it but in any other way the equation is non-factorable.
2008-07-11 4:08 pm
it can't be factored, if you graph it you will see I'm right
2008-07-11 4:07 pm
i don't understand ur pro
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