4а) х^2-10х+21=х^2-3х-7х+21=
=(х^2-3х)-(7х-21)=х(х-3)-7(х-3)=
=(х-3)(х-7)
4б) 5у^2+9у-2=5у^2+10у-у-2=
=(5у^2+10у)-(у+2)=5у(у+2)-(у+2)=
=(у+2)(5у-1)
5,06-0,24=4,82дм(4дм,8см,2мм)
1) 3*10⁻¹+5*10⁻³+4*10⁻⁴ = 0,3+0,005+0,0004 = 0,3054.
F`(x)=(1/3ctg15x)`*(15x)~+(√3)`=-1/3sin²15x)*15+0=-5/sin²15x
F`(π/4)=-5/sin²(15π/4)=-5/sin²(4π-π/4)=-5/sin²(-π/4)=-5:(√2/2)²=
=-5:(1/2)=-10