Во вложении..................
cos a = +- 4/5
tg a = +- 3/4
ctg a = +- 4/3
1)(2a+b)^2-(a-2b)^2=
4a^2+4ab+b^2-a^2+4ab-4b^2=
3a^2+8ab+3b^2
2)(x+y)^2-(y-z)^2=
x^2+2xy+y^2-y^2+2yz-z^2=
x^2+2xy+2yz-z^2
181818 : 54 - 818181 : 243 =
= 181818 : (18· 3) - 818181 : (81 ·3) =
= 181818 : 18 : 3 - 818181 : 81 : 3 =
= 10101 : 3 - 10101 : 3 = 0
<span>Х²-2х-35=0
D = (-2)</span>² - 4*1*(-35) = 4 + 140 = 144; 12² = 144
x1 = (-(-2) + 12)/ 2 = 7
x2 = (-(-2) - 12)/ 2 = - 5