SOLUTION: Hi guys, f(x)=x^2+2x+15 Find all complex numbers for which f(x)=0 I'm at a loss here, I know this should be really easy but after summer I'm at a loss for how to do this. If

Algebra ->  Complex Numbers Imaginary Numbers Solvers and Lesson -> SOLUTION: Hi guys, f(x)=x^2+2x+15 Find all complex numbers for which f(x)=0 I'm at a loss here, I know this should be really easy but after summer I'm at a loss for how to do this. If      Log On


   

Question 892833: Hi guys,
f(x)=x^2+2x+15
Find all complex numbers for which f(x)=0
I'm at a loss here, I know this should be really easy but after summer I'm at a loss for how to do this. If anyone has any help I'd really appreciate it,preferably with an explanation of the steps. Thanks in advance
Answer by AnlytcPhil(1806) About Me  (Show Source):
You can put this solution on YOUR website!
f%28x%29=x%5E2%2B2x%2B15

x%5E2%2B2x%2B15%22%22=%22%22%220%22

x%22%22=%22%22%28-b+%2B-+sqrt%28+b%5E2-4ac+%29%29%2F%282a%29+

x%22%22=%22%22%28-2+%2B-+sqrt%28+2%5E2-4%2A1%2A15+%29%29%2F%282%2A1%29+

x%22%22=%22%22%28-2+%2B-+sqrt%284-60+%29%29%2F2+

x%22%22=%22%22%28-2+%2B-+sqrt%28-56%29%29%2F2+

x%22%22=%22%22%28-2+%2B-+i%2Asqrt%2856%29%29%2F2+

x%22%22=%22%22%28-2+%2B-+i%2Asqrt%284%2A14%29%29%2F2+

x%22%22=%22%22%28-2+%2B-+i%2Asqrt%284%29%2Asqrt%2814%29%29%2F2+

x%22%22=%22%22%28-2+%2B-+i%2A2%2Asqrt%2814%29%29%2F2+

x%22%22=%22%22%282%28-1+%2B-+i%2Asqrt%2814%29%29%29%2F2+

x%22%22=%22%22%28cross%282%29%28-1+%2B-+i%2Asqrt%2814%29%29%29%2Fcross%282%29+

x%22%22=%22%22-1+%2B-+i%2Asqrt%2814%29+

All complex numbers for which f(x)=0 are -1+%2B+sqrt%2814%29i+, -1+-+sqrt%2814%29i+, 

Edwin