Все что знаю
(^ - степень)
1.a^2-8a-9
4.(x+y)(x-y)(x^2+xy+y^2)
5.d) (5m-2)(21m-16)
f)(3x+11y)(9x^2 - 15xy + 67y^2)
Смотри....................
9x²-7x²-21x+2x+6+12-1=0
2x²-7x²+5=0
D=9
x1=7+√9/2×2
x1=2.5
x2=7-√9/2×2
x2=1
Sin^2 x–2cos x*sin x+cos^2 x=1 / cos^2 x
sin^2 x/cos^2 x –2cos x*sin x/cos^2 x +cos^2 x/cos^2 x=1
tg^2 x - 2tg x + 1 - 1 = 0
Вводим новую переменную: tg x = y
y^2 - 2y =0
y(y - 2) = 0
y1=0 или y-2 = 0
y2=2
tg x = 0
x = arctg 0 +πk
x = πk
tg x = 2
x=arctg 2 + πk
Ответ: x = πk; x=arctg 2 + πk
Log(4x+5) = 2 + log(x-4) => log(4x + 5) - log(x - 4) = 2
=> log((4x + 5) / (x - 4)) = 2
=> (4x + 5) / (x - 4) = 25
=> 4x + 5 = 25x - 100
=> 21x = 105
=> x = 5