Please help and please explain !

x= -28.173

Step-by-step explanation:

formula for quadratic equation, y= (-b±√(b²-4ac))/(2a)

a= 1, b= -4 and c= -1

y= 4 + √(16+4)

= 4 + √20

here,

sinx = y

sinx = 4+ √20

or, x= sin^-1 (4+√20)

which doesn't exist

taking

sinx = 4-√20

x = -28.173°