Tga*ctga -(-sina)*(-sina)=1-sin^2a=cos^2a
В) а-d
-------------------------------------------
d=23-26=-3
a12=a1+11d=26+11*(-3)=-7
S12=(a1+a12)/2 * 12= (26-7)/2 * 12 =114
Ответ: 114
U=v-10
2(v-10)+3v=15, 2v-20+3v=15
5v=20+15, 5v=35
v=7
u=7-10, u=-3
/u,v/=/-3,7/
a)b(m-7)-7b=bm-7b-7b=bm-14b
б)x(c+1)+c(x-1)=cx+x+cx-c=x+2cx-c
в)y(x-4)+x(3-y)=xy-4y+3x-xy=3x-4y
г)m(k-3)-k(m-5)=km-3m-km+5k=5k-3m
д)a(1-b)-a(1+b)=a-ab-a-ab=-2ab
е)b(2d-5)-b(d+5)=2bd-5b-bd-5b=bd-10b