9) 6*sin²a + 8*cos²a = 7
6*sin²a + 6*cos²a + 2*cos²a = 7
6*1 + 2*cos²a = 7
( sin²a + cos²a = 1 основное тригонометрическое тождество)
2*cos²a = 1
cos²a = 1/2
sin²a = 1-cos²a = 1-(1/2) = 1/2
tg²a = sin²a / cos²a = 1
5) πx/4 = (-π/4) + 2πk, k∈Z πx/4 = (-3π/4) + 2πn, n∈Z
x = -1 + 8k, k∈Z x = -3 + 8n, n∈Z
k=1: x = 8-1=7 n=1: x = 8-3=5 -это ответ))
а10-а4=-90 a1+9d-a1-3d=-90 6d=-90 d=-15
a6=-55 a1+5d=-55 a1+5*(-15)=-55 a1=-55+75=20
1
3a+3-na-n=3(a+1)-n(a+1)=(a+1)(3-n)
2
(x²-y²)/(3x-2x²+3y-2xy)=(x-y)(x+y)/[3(x+y)-2x(x+y)]=(x-y)(x+y)/[(x+y)(3-2x)]=
=(x-y)/(3-2x)
3
y=x² парабола
х -4 -3 -2 -1 0 1 2 3
у 16 9 4 1 0 1 4 9
у=-3х+4
х -4 1
у 16 1
Ответ х=-4,х=1