Answer:
A quadratic equation can be written as:
a*x^2 + b*x + c = 0.
where a, b and c are real numbers.
The solutions of this equation can be found by the equation:

Where the determinant is D = b^2 - 4*a*c.
Now, if D>0
we have the square root of a positive number, which will be equal to a real number.
√D = R
then the solutions are:

Where each sign of R is a different solution for the equation.
If D< 0, we have the square root of a negative number, then we have a complex component:
√D = i*R

We have two complex solutions.
If D = 0
√0 = 0
then:

We have only one real solution (or two equal solutions, depending on how you see it)
Answer: option C is the correct answer
Step-by-step explanation:
The system of linear equations is
10x + 7y = 12 - - - - - - - 1
8x + 7y = 18 - - - - - - - 2
Since the coefficient of y is the same in equation 1 and equation 2, we will eliminate y by subtracting equation 2 from equation 1, it becomes
10x - 8x + 7y - 7y = 12 - 18
2x = -6
x = - 6/2 = - 3
Substituting x = - 3 into equation 1, it becomes
10×-3 + 7y = 12
-30 + 7y = 12
Let the constants be on the right hand side and the term containing y be on the left hand side. It becomes
7y = 12 + 30
7y = 42
y = 42/7
y = 6
C) (−3, 6)