Пожалуйста, помогите, очень срочно!

b[n]=b[1]*q^ (n-1) b[1]=-1/27b[2]=b[1]*qb[2]=-1/27qb[3]=b[1]q^2b[3]=-1/27q^2b[4]=b[1]q^3b[4]=-1/27q^3b[5]=b[1]q^4b[5]=-1/27q^4 b[1]*b[2]*b[3]*b[4]*b[5]=-1/243-1/27*(-1/27) q*(-1/27) q^2*(-1/27) q^3*(-1/27) q^4=-1/243 (-1/27) ^5*q^ (1+2+3+4)=-1/243 (-1/3) ^3) ^5*q^10=(-1/3) ^5 (-1/27) ^5*(q^2) ^5=(-1/3) ^5 (-1/27q^2) ^5=(-1/3) ^5-1/27q^2=-1/3q^2=-1/3*(-27) q^2=9q<0q=-3