1) ( 12.7 х - 1.5 ) - ( 3.1х - 1.4 ) = 12.7 х - 1.5 - 3.1х+ 1.4= 9.6х - 0.1
2) ( у-8 ) 2 ( два это степень )
7a²-2a-3=7(a-(1-√22)/7)(a-(1+√22)/7)=1/7(a-1+√22)(a-1-√22)
D=4+84=88
a1=(2-2√22)/14=(1-√22)/7
a2=(1+√22)/7
7a²-6a-1=7(a+1/7)(a-1)=(7a+1)(a-1)
D=36+28=64
a1=(6-8)/14=-1/7
a2=(6+8)/14=1
(7a²-2a-3)/(7a²-6a-1)=((a-1+√22)(a-1-√22)/[7(7a+1)(a-1)]
Х+(х+42)=90
2х+ 42=90
2х=90-42
2х=48
х=24
один угол 24, второй 24+42=66(66+24= 90)