8-3.8x+0.2x=0.8
-3.6x=0.8-8
-3.6x=-7.2
x=2
1 задача
12÷2=6 дм- довжина стрiчок
2 задача
12÷2=6 частин-
314 х 75 = 23550 - верно
601 х 852 = 512052 - верно
1/(1-tga)-1/(1+tga)-tg2a=1/(1-tga)-1/(1+tga)-2tga/(1-tg²a)=
=(1+tga-1+tga-2tga)/(1-tg²a)=0/(1-tg²a)=0
cos36cos72-1/4=2sin36cos36cos72/2sin36 -1/4=sin72cos72/2sin36 -1/4=
=sin144/4sin36 -1/4=sin(180-36)/4sin36 -1/4=sin36/4sin36 -1/4=1/4-1/4=0
А(b+c)=ab+ac
a(b-c)=ab-ac
a)57.48*0.9093+42.52*0.9093=0.9093(57.48+42.52)=0.9093*100=90.93
б) 6.395*835.67+6.395*164.33=6.395(835.67+164.33)=6.395*1000=6395
в) 104.76*378.91-94.76*378.91=378.91(104.76-94.76)=378.91*10=3789.1
г) 0.78*496.6-396.6*0.78=0.78(496.6-396.6)=0.78*100=78