Answer:
D
Explanation:
We will solve the equation by using quadratic formula.
x= (-b ± √(b^2-4ac))/2a
The standard form of quadratic equation is:
ax^2+bx+c=0
So by comparing with the standard form, we get:
a=1
b= -4
c=18
Putting the values in the formula
x= (-(-4)± √((-4)^2-4(1)(18)))/2(1)
x = (4± √(16-72))/2
x = (4± √(-56))/2
The minus sign in square root will introduce the imaginary symbol.
x = (4± √(14*4*(-1)))/2
The minus 1 can be replace by the imaginary i => i^2 = -1
x = (4± √(14*2^2*i^2 ))/2
The terms with squares can be brought out of the square root
So,
x = (4± 2i√14)/2
Taking 2 as common
x = (2(2± i√(14)))/2
x = 2± i√14