![Tont B]()
Using standard for of y=ax^2+bx+c
Where x =(-b+-sqrt(b^2-4ac))/(2a)
Let:
a=-4
b=-4
c=-15
So by substitution we have:
x= (-(-4) +- sqrt((-4)^2 -(4)(-4)(-15)))/(2(-4)
x=(+4 +- sqrt(16-240))/(2(-4))
x=(4+-sqrt(-224))/(-8)
partitioning 224 into prime numbers and squaring where able
x= (4+- sqrt((-1) times 2^2 times 2^2 times 2 times 7))/(-8)
x= (4+-4sqrt(-14))/(-8)
x=(1+- i sqrt(14))/(-2)
As we have +- in the numerator before the root having a negative denominator makes no tangible difference to that root. However, it does have an effect on the 1 preceding it. Consequently we have -1/2.
x=-1/2 +- isqrt(14/4)
x=-1/2 +-isqrt(7/2)
