Quick Complex No. Questions (1 Viewer)

[FroZenWaffleS]

Got some more dilemmas

1) Without calculating a,b and c evaluate -b/a and c/a if one of the equation
ax^2 +bx + c = 0 is:

2 +i

2) find the complex factor of:
x^2 + 4x + 5

3) Express as partial fractions with complex linear denominators:

1/ (x^2 +1)

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Once again if anyone is bothered, please show working. Thank you
You might also notice this post from some other thread but i just started a new thread because that other thread looks like not a asking for homework help thread.

 

[haboozin]

Got some more dilemmas

1) Without calculating a,b and c evaluate -b/a and c/a if one of the equation
ax^2 +bx + c = 0 is:

2 +i

2) find the complex factor of:
x^2 + 4x + 5

3) Express as partial fractions with complex linear denominators:

1/ (x^2 +1)

--------------------------------------------------------------------------------
Once again if anyone is bothered, please show working. Thank you
You might also notice this post from some other thread but i just started a new thread because that other thread looks like not a asking for homework help thread.

1) Without calculating a,b and c evaluate -b/a and c/a if one of the equation
ax^2 +bx + c = 0 is:

2 +i

umm... this question is wrong, u can only do this if a, b and c are real... but we dont know that... i think they ment if they are real.

so if a, b, c, are real
and 2 + i is a root then 2 - i is a root (remember how if Z is a root then Z (line on top = conjacute) is also a root.

so -b/a = sum of roots
2 + i + 2 - i = 4

c/a = product of roots = 5

2) find the complex factor of:
x^2 + 4x + 5

use the quadratic formula

(-4 +- 2i)/2

so (2x + 4 + 2i)(2x + 4 - 2i)

3) Express as partial fractions with complex linear denominators:

1/ (x^2 +1)

donno what that means?

i think it would be something liek this, otherwize stupid question.
1/(x - i)(x + i)

sp 1/(x - i) x 1/(x + i)

dont think it would want u to rationalize.