D = 64 - 4*1*15 = 4
V D = 2
X1 = ( - 8 + 2 ) : 2 = (- 3 )
X2 = ( - 5 )
...................................
X^2 + 8X + 15 = ( X + 3)*( X + 5 )
1)a(x-y)+4(x-y)=(х-у)(а+4)
2) 3x-3y+ax-ay=3(х-у)+а(х-у)=(х-у)(3+а)
4sin²x -5sinxcosx - 6cos²x=0|:cos²x≠0
4tg²x-5tgx-6=0 |t=tgx
4t²-5t-6=0
D=(-5)²-4*4*(-6)=25+96=121=11²
t1=(5+11)/8=2 t2=(5-11)/8=-0,75
tgx=2 tgx=-0,75
x=arctg2+πn, n∈Z x=-arctg0,75+πn, n∈Z