<span>-4 (2,5а-1,5)+5,5а-8 = -1</span>
за т. Герона: b=a+c будет x1=-1;
<span>1)(cos36°+sin^2 18°)/cos18°=(сos²18-sin²18+sin²18)/cos18=cos²18/cos18=cos18
2)cos80°/(cos40°+sin40°)(cos²40-sin²40)/(cos40+sin40)=</span>
=(cos40-sin40)(cos40+sin40)/<span>(cos40+sin40)=cos40-sin40</span>
72:100=0,72 (1%)
0,72*25=18 (25%)
2x^2-10x = 0
2x(x - 5) = 0
1) 2x = 0
x = 0
2) x - 5 = 0
x = 5