А(1)=4,2
а(2)=3,5
d=3.5-4.2=-0.7
a(12)=a(1)+11d
a(12)=4.2-7.7=-3.5
S(12)=(a(1)+a(12)) * n / 2 = (4.2-3.5)*12/2=0.7*6= 4.2
1/2* arcsin√3/2-2*arccos (-1/2)=1/2*π/3-2*2π/3=π/6-4π/3=-7π/6
<span> 2x^2-x+3=4
2x^2-x=1
теперь сам пример
</span>6x^2(2x^2-x+3)-3x(2x^2-x+3)=(6x^2-3x)*(2x^2-x+3)=3*(2x^2-x)*(2x^2-x+3)=3*1*4=12
<span>=((m²-10m)-(6m-64))/(m²-64)=(m²-16m+64)/(m-8)(m+8)=(m-8)(m-8)/</span><span>(m-8)(m+8)=
=(m-8)/(m+8)
</span>