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

Algebra ->  Rational-functions -> SOLUTION: 9X^2+9=0 A.-1,1 B.-1i,1i c. 3i,3i d. -9i,9i       Log On


   

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) About Me  (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

ax%5E2%2Bbx%2Bc=0

the general solution using the quadratic equation is:

x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29



So lets solve 9%2Ax%5E2%2B9=0 (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 9%2Ax%5E2%2B0%2Ax%2B9=0 notice a=9, b=0, and c=9)




x+=+%280+%2B-+sqrt%28+%280%29%5E2-4%2A9%2A9+%29%29%2F%282%2A9%29 Plug in a=9, b=0, and c=9



x+=+%280+%2B-+sqrt%28+0-4%2A9%2A9+%29%29%2F%282%2A9%29 Square 0 to get 0



x+=+%280+%2B-+sqrt%28+0%2B-324+%29%29%2F%282%2A9%29 Multiply -4%2A9%2A9 to get -324



x+=+%280+%2B-+sqrt%28+-324+%29%29%2F%282%2A9%29 Combine like terms in the radicand (everything under the square root)



x+=+%280+%2B-+18%2Ai%29%2F%282%2A9%29 Simplify the square root (note: If you need help with simplifying the square root, check out this solver)



x+=+%280+%2B-+18%2Ai%29%2F%2818%29 Multiply 2 and 9 to get 18



After simplifying, the quadratic has roots of


x=i or x=+-+i


So the answer is B)

Answer by stanbon(75887) About Me  (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) About Me  (Show Source):
You can put this solution on YOUR website!
9X%5E2%2B9=0

Divide both sides by 9

x%5E2%2B1=0

Add -1 to both sides

x%5E2=-1

Take the root of both sides

x=sqrt%28-1%29

x=i or x=-i

Answer b.