What's happening is that every subtraction can be written as "addition of the opposite."
18-5 = 18 + (-5)
One reason this is done in the work you showed is that they're trying to show why you distribute the negative and the 1 into the parentheses, why you multiply everything in the parentheses by "-1" and not just 1.
The other reason is to later to be able to move the individual terms around, so you'll be able to combine like terms.
When you move terms around, the sign has to stay attached to the term, so writing all the subtractions as addition helps keep the sign attached.
X^2 = 9x + 6
x^2 - 9x - 6 = 0
use quadratic formula : (-b (+-) sqrt b^2 - 4ac) / (2a)
a = 1, b = -9, c = -6
now we sub
x = (-(-9) (+-) sqrt -9^2 - 4(1)(-6)) / 2(1)
x = 9 (+-) sqrt 81 + 24)/2
x = 9 (+-) sqrt 105) / 2
x = 9/2 + 1/2 sqrt 105 or x = 9/2 - 1/2 sqrt 105
Answer:
Step-by-step explanation:
Given
The given system is 
can be represented by
The given system is consistent when determinant of A is not equal to zero
i.e. system is consistent for all value of k except 
Answer:
A. 2, 3, and 4
B: 4
Step-by-step explanation:
