Ответ:
х²+8х+16-9а² = (х+4)²-9а² = (х+4+3а)(х+4-3а)
2) cosx = -√2/2
x = +-3π/4 + 2πk, k∈Z
x∈(0;2π)
x = 3π/4; x=5π/4
второй вариант ответа
3) cos(4x)*cos(5x) = cos(6x)*cos(7x)
0.5*(cos(4x-5x) + cos(4x+5x)) = 0.5*(cos(6x-7x) + cos(6x+7x))
cos(x) + cos(9x) = cos(x) + cos(13x)
cos(13x) - cos(9x) = 0
-2sin(11x)*sin(2x) = 0
sin(11x) = 0, 11x = πk, x = πk/11, k∈Z
sin(2x) = 0, 2x = πk, x = πk/2, k∈Z
x∈[0;π/2]
0≤πk/11≤π/2
0≤k≤11/2, k∈Z
k=0, 1, 2, 3, 4, 5
x=0, x=π/11, x=2π/11, x=3π/11, x=4π/11, x=5π/11
0≤πk/2≤π/2
0≤k≤1, k∈Z
k=0, 1
x=0, x=π/2
Сумма корней: 0 + (π/11) + (2π/11) + (3π/11) + (4π/11) + (5π/11) + 0 + (π/2) = (15π/11) + (π/2) = (30π + 11π)/22 = 41π/22
последний вариант ответа
1.1) x^2+16-8x
2) 9x^2+25-30x
3)4a^2+6a-6a-9=4a^2-9
4)y^4+2y^2-2y^2-4=y^4-4
3.6ab-9b^2+a^2+9b^2-6ab=a^2=(-2/7)|^2=4/49
4.1)5*(4-9х^2y^2)=20-45x^2y^2
2)a^6-b^4
3)x^2+y^2+2xy-x^2-y^2+2xy=4xy
5. 36a^2-1-36a^2-8a=1
-1-8a=1
-8a=2
8a=-2
a=-2/8=-1/4
номер 1: 9/4 + 4/5 -1 = 5/2
номер 2: в числителе будет 7 в знаменателе 7 : 1/7 + 49
номер 3: 1/х^8