-п\2+2пн
нЭZ
cosx*cosx=1-sinx*sinx=(1-sinx)(1+sinx)
а₁ = 8
а₁₂ = 29
Найти S₁₅
1)
a₁₂ = a₁+ 11d
29 = 8 + 11d
11d = 21;
d = 21/11
2)
a₁₅ = a₁ + 14d
а₁₅ = 8 + 14*21/11= (88+294)/11 = 382/11
3)
S₁₅ = (a₁+a₁₅) * 15/2
S₁₅ = (8+382/11) * 15/2 = 470/11*15/2= 3525/11=320 5/11
Ответ: 320 ⁵/₁₁
1).6x^2-4xy-y^2-4x^2-y^2=2x^2-4xy-2y^2. 2).125x^3y^4*(-1/5x^2y)^3=125x^3y^4*(-1/125x^6y^3)= -x^9y^7.