pliss kali no 1-4 dan 8 dikerjain ya plis kali

1.) x^2 -5x -4 > 10
x^2 -5x -4 -10 >0
x^2 -5x -14 > 0
(x-7) (x +2) >0
x=7 atau x=-2
3.) -> 2x +4 > x-3 akar dihilangkn
x > -7 pindah ruas
-> √2x +4 > 0
2x +4 > 0 dikuadratkn
x > -2
8.) AB = b-a
=(4,1,3) -(2,-1,4)
=(2,2,-1)
AC = c-a
= (2,0,5) -(2,-1,4)
=(0,1,1)
a . b = (2,2,-1) x (0,1,1)
=(0, 2,-1) = 0+2-1 =1
|a| = √0+4+1 =√5
|b| =√0+1+1 =√2

cos = a . b / |a| |b|
=1/√5 x √2
=1/√10 -> 1/10 √10

#maaf kalo salah, soalnya cos segitu gak tau berapa sudutnya.. =-)