Let's perform the synthetic division
color(white)(aaaa)4|color(white)(aaaa)-4color(white)(aaaa)-15color(white)(aaaaaa)-4color(white)(aaaaa)-12
color(white)(aaaaa)|color(white)(aaaa)color(white)(aaaaaaa)-16color(white)(aaaa)-124color(white)(aaaa)-512
color(white)(aaaaaaaaa)_________
color(white)(aaaaaa)|color(white)(aaaa)-4color(white)(aaaa)-31color(white)(aaaa)-128color(white)(aaaa)color(red)(-524)
The remainder is =-524 and the quotient is =-4x^2-31x-128
ALSO,
Apply the remainder theorem
When a polynomial f(x) is divided by (x-c), we get
f(x)=(x-c)q(x)+r
Let x=c
Then,
f(c)=0+r
Here,
f(x)=-4x^3-15x^2-4x-12
Therefore,
f(4)=-4*4^3-15*4^2-4*4-12
=-256-240-16-12
=-524
The remainder is =-524