вот так вот
1) 7х - 21 < 0 2) 3x + 12 < 3
5x + 10 > 0 11 - 5x > 26
7x < 21 3x < - 9
5x > - 10 - 5x > 15
x < 3 x < - 2
x > -2 x > - 3
0/\/\/\/\0> x 0/\/\\/\/\\/\0> x
-2 3 -3 -2
x є ( -2 ； 3 ) х є ( -3 ； -2 )
sin²x + 2sinx×cosx - 3cos²x + 2 = 0
sin²x + 2sinx×cosx - 3cos²x + 2×1 = 0
sin²x + 2sinx×cosx - 3cos²x + 2(sin²x + cos²x) = 0
sin²x + 2sinx×cosx - 3cos²x + 2sin²x + 2cos²x = 0
3sin²x + 2sinx×cosx - cos²x = 0 | ÷ cos²x
3tg²x + 2tan x - 1 = 0
Пусть tg x = a, тогда:
3a² + 2a - 1 = 0
D = 2² - 4×3×(-1) = 4 + 12 = 16
x₁ = -2+√16/2×3 = -2+4/6 = 2/6 = 1/3
x₂ = -2-√16/2×3 = -2-4/6 = -6/6 = -1
tg x = 1/3 или tg x = -1
x₁ = arctg(1/3) + πn x₂ = arctg(-1) + πn
x₁ = 0,321751 + πn x₂ = 3π/4 + πn
x₁ = 18,4° + πn, n∈Z x₂ = 135° + πn, n∈Z
=a^+6a+9-(b^2-14b+49)=a^2+6a+9-b^2+14b-49=a^2-b^2+6a+14b-40