B1 = - 7
b2 = - 28
q = b2/b1 = 4
b3 = b1*q^(2) = ( - 7)*16 = - 112
S5 = ((-7)*(1 - 4^5))/(1 - 4) = - 2387
1)18*(-9)^ -1=18*(-1/9)=-2
2)0/5^-2+(1/4)^ -1=4+4=8
3) 10^2 *(1/50)^ -1=100*50=5000
1234:10=123,4. Остаток 4.
cos2x=1-2sin^2*x заменим
(1-sin^2*x)+2sinx+2=0
-2sin^2*x+2sinx+3=0
sinx=t
-2t^2+2t+3=0
пример точно правильный?