k^2-k=2, how to find k?

k^2 - k = 2

k^2 - k - 2 = 0

Method 1: by calculator, you know la!!!

Method 2: Factorization

k^2 - k - 2 = 0

k^2 - 2k + k - 2 = 0

k(k - 2) + (k - 2) = 0

(k + 1)(k - 2) = 0

k = -1 or 2

Method 3: by quadraic formula

k^2 - k - 2 = 0

k = 1 +- sqrt(1 + 8) / 2

= 1 +- sqrt9 / 2

= (1 + 3) / 2 or (1 - 3) / 2

= 4 / 2 or -2/2

= 2 or -1

k^2-k=2
k^2-k-2=0
Completing Square:
(k-0.5)^2-2.25=0
(k-0.5)^2-1.5^2=0
(k-0.5+1.5)(k-0.5-1.5)=0
(k+1)(k-2)=0
k=-1 or k=2