Question 277147
1) x squared - 4x + 5 = 0

x^2 - 4x + 5 = 0
use ax^2 + bx + c = 0
a = 1, b = -4, c = 5
{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}
{{{x = (4 +- sqrt( 16 - 4*5 ))/2 }}}
{{{x = (4 +- sqrt( 16 - 20 ))/2 }}}
{{{x = (4 +- sqrt( -4 ))/2 }}}
{{{x = (4 +- 2i)/2 }}}
{{{x = 2 +- i }}}
check: (2+i)^2 - 4(2+i) + 5 = 0
       4 + 4i - 1 - 8 - 4i + 5 = 0
       4 - 1 - 8 + 5 + 4i - 4i = 0
           3 - 8 + 5 = 0
             - 5 + 5 = 0
                   0 = 0
       (2-i)^2 - 4(2-i) + 5 = 0
        4 - 4i - 1 - 8 + 4i + 5 = 0
        4 - 1 - 8 + 5 = 0
            3 - 8 + 5 = 0
              - 5 + 5 = 0
                    0 = 0

2) C squared + 6c + 8 = 0 

c^2 + 6c + 8 = 0
(c+2)(c+4) = 0 (using foil this does come out to the above)
c = -2 or c = -4

3) a squared - 2a = -1 

a^2 - 2a = -1
a^2 -2a + 1 = 0
(a-1)(a-1) = 0 
one answer a=1

4) n squared - 7n = -10

n^2 - 7n = -10
n^2 - 7n + 10 = 0
(n - 2)(n - 5) = 0
n = 2 or n = 5