(-17tg4⁰ -2tg176⁰)/(4ctg274⁰-ctg94⁰)=
=(-17tg4⁰-2tg(180⁰-4⁰)/(4ctg(270⁰+4⁰)-ctg(90⁰+4⁰)=
=(-17tg4⁰+2tg4⁰)/(4tg4⁰-tg4⁰)=(-15tg4⁰)/3tg4⁰=-5;
D=(x4-x2):2=(-1-7):2=-4
x1=x2-d=7-(-4)=11
S8=(2*11-4*7)*8/2=(22-28)*4=(-6)*4=-24
A>5⇒2a>10
b>1 U c>3⇒3bc>9
2a+3bc>19
19>15⇒3a+3bc>15