SOLUTION: 9X^2+9=0 A.-1,1 B.-1i,1i c. 3i,3i d. -9i,9i

Question 119189: 9X^2+9=0
A.-1,1
B.-1i,1i
c. 3i,3i
d. -9i,9i

Found 3 solutions by jim_thompson5910, stanbon, solver91311:
Answer by jim_thompson5910(35256)   (Show Source): You can put this solution on YOUR website!
Let's use the quadratic formula to solve for x:

Starting with the general quadratic

the general solution using the quadratic equation is:

So lets solve (note: since the polynomial does not have an "x" term, the 2nd coefficient is zero. In other words, b=0. So that means the polynomial really looks like notice , , and )

Plug in a=9, b=0, and c=9

Square 0 to get 0

Multiply to get

Combine like terms in the radicand (everything under the square root)

Simplify the square root (note: If you need help with simplifying the square root, check out this solver)

Multiply 2 and 9 to get 18

After simplifying, the quadratic has roots of

or

So the answer is B)
Answer by stanbon(75887)   (Show Source): You can put this solution on YOUR website!
9X^2+9=0
9(x^2+1)=0
x^2+1 = 0
(x+i)(x-i) = 0
x = -i or x = i
======================
Cheers,
Stan H.
Answer by solver91311(24713)   (Show Source): You can put this solution on YOUR website!

Divide both sides by 9

Add -1 to both sides

Take the root of both sides

or

Answer b.
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