3х-4+9х²-12х-9х²+4х=0
-5х=4
5х=-4
х=-4/5
Ответ:-0,8.
Sinx,cosx≠0 x≠π/2 *n n∈Z
обозначим tgx=z ⇒2z-3*1/z -1=0
2z^2-z-3=0 D=1+4*3*2=1+24=25 √D=5 z1=1/4*(1+5)= 6/4=3/2
z2=1/4*(1-5)=-1
tgx=3/2 x=arctg(3/2)+πn
tgx=-1 x=argtg(-1)+πk= -π/4+πk n,k∈Z
ответ: x=arctg(3/2)+πn, x=-π/4+πk
A1 = 5an+1 = an - 3a10 — ? a2 = 5 – 3 = 2a3 = 2 – 3 = -1a4 = -1 – 3 = -4a5 = -4 – 3 = -7a6 = -7 – 3 = -10a7 = -10 – 3 = -13a8 = -13 – 3 = -16a9 = -16 – 3 = -19a10 = -19 – 3 = -22<span> </span>