(2cos²x-1)(2cosx+1)+1=0
4cos³x+2cos²x-2cosx-1+1=0
2cosx(2cos²x+cosx-1)=0
cosx=0⇒x=π/2+πn
2cos²+cosx-1=0
cosx=a
2a²+a-1=0
D=1+8=9
a1=(-1-3)/4=-1⇒cosx=-1⇒x=π+2πn
a2=(-1+3)/4=1/2⇒cosx=1/2⇒x=+-π/3+2πn
x=π/2+πn;x=π+2πn;x=+-π/3+2πn
<span>6x^2-6x-12=0
6(x^2-x-2)=0
6(x^2+x-2x-2)=0
6(x*(x+1)-2(x+1))=0
6(x-2)*(x+1)=0
(x-2)*(x+1)=0
x-2=0 x=2
x+1=0 x=-1
</span>
а) x*(x+2)*(x-3)<0
x₁=-2 x₂=0 x₃=3
-∞__-__-2__+__0__-__3__+__+∞
x∈(-∞;-2)U(0;3).
Б) (2x+1)(3-x)(x+5)≥0
x₁=-5 x₂=-0,5 x₃=3
-∞__+__-5__-__-0,5__+__3__-__+∞
x∈(-∞;-5]U[-0,5;3].
<span>80+0,4*(-10)</span>³<span>=80+0.4*(-1000)=80+(-400)=-320</span>