Hi, can anyone show me how to do this problem? 100 points for this. in advance

z^2 + (-1 + 5·i)·z + 14 - 7·i = 0

1+2i  is a root

z= 1+2i

z^2 = (1+2i) (1+2i)

       = 1 +2i+2i +4i^2

       = 1 +4i -4

       = -3+4i

= (-1+5i) (1+2i)

-1+5i-2i+10i^2

  -1+3i-10

  -11+3i                

z^2 + (-1 + 5·i)·z + 14 - 7·i = 0

-3+4i  + -11+3i +14 - 7i

Combine like terms

-3-11 +14 +4i +3i-7i

0

So 1+2i is a root

1-2i  is not a root

z= 1-2i

z^2 = (1-2i) (1-2i)

       = 1 -2i-2i +4i^2

       = 1 -4i -4

       = -3-4i

= (-1+5i) (1-2i)

-1+5i+2i-10i^2

  -1+7i+10

  9+7i                

z^2 + (-1 + 5·i)·z + 14 - 7·i = 0

-3-4i  + 9+7i +14 - 7i

Combine like terms

-3+9 +14 -4i +7i-7i

20 -4i

So 1-2i is not a root

The complex conjugate being roots is only true for real coefficients

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional

what is the information provided?

step-by-step explanation: