1) xn=3n-23n-2>123n>14n>14/3n=52) b1=1; b4=b1*q^3=8b1q^3/b1=8/1q^3=8q=2b2=b1q=2b3=b2q=41;2;4;83) b2+b5=9b3+b4=6b1q+b1q^4=9b1q^2+b1q^3=6b1q(1+q^3)=9b1q^2(1+q)=6b1q(1+q^3)/b1q^2(1+q)=9/6(1+q)(q^2-q+1)/q(1+q)=3/2(q^2-q+1)/q=1.5q^2-q+1=1.5qq^2-2.5q+1=0D=6.25-4=2.25q=(2.5+1.5)/2=4/2=2q=(2.5-1.5)/2=1/2=0.51) q=2:b1=6/q^2(1+q) = 6/(4*3)=6/12=0.5b7=b1q^6=0.5*64=322) q=0.5:b1=6/q^2(1+q)=6/(0.25*1.5)=24/1.5=48/3=16b7=b1q^6=16*2^(-6)=2^4*2^(-6)=2^-2=0.25ответ: 32; 0.25 4) bn=3^(n-1)b1=3^0=1b2=3^1=3q=b2/b1=3/1=3S4=b1*(q^4-1)/(q-1)=1*(81-1)/(3-1)=80/2=40
а) (с+2)(с-3)-(с+1)(с+3) = (c^2 + 2c - 3c - 6) - (c^2 + c + 3c + 3)== c^2 - c - 6 - ( c^2 + 4c + 3) = c^2 - c - 6 - c^2 - 4c - 3 = 3 - 5c.
б) (р+3)(р-11)+(р+6)^2 = (p^2 + 3p - 11p - 33) + (p^2 + 12p + 36) = p^2 - 8p - 33 + p^2 + 12p + 36 = 2p^2 + 4p + 3.
в) (4х-3)^2+6х(4-х) = 16x^2 - 24x + 9 + 24x - 6x^2 = 10x^2 + 9.
г) (b+3)(b-3)+(2b+3)^2 = b^2 + 3b - 3b - 9 + 4b^2 + 12b + 9 = 5b^2 + 12b.
д) (а-5)(а+1)-(а-6)(а-1) = a^2 - 5a + a - 5 - (a^2 - 6a - a + 6) = a^2 - 4a - 5 - (a^2 - 7a + 6) = a^2 - 4a - 5 - a^2 + 7a - 6 = 3a - 11.
е) (a-4)(a+4)-2a(3-a) = a^2 - 4a + 4a - 16 - 6a + 2a^2 = 3a^2 - 6a - 16.
1) xn=3n-2
3n-2>12
3n>14
n>14/3
n=5
2) b1=1; b4=b1*q^3=8
b1q^3/b1=8/1
q^3=8
q=2
b2=b1q=2
b3=b2q=4
1;2;4;8
3) b2+b5=9
b3+b4=6
b1q+b1q^4=9
b1q^2+b1q^3=6
b1q(1+q^3)=9
b1q^2(1+q)=6
b1q(1+q^3)/b1q^2(1+q)=9/6
(1+q)(q^2-q+1)/q(1+q)=3/2
(q^2-q+1)/q=1.5
q^2-q+1=1.5q
q^2-2.5q+1=0
D=6.25-4=2.25
q=(2.5+1.5)/2=4/2=2
q=(2.5-1.5)/2=1/2=0.5
1) q=2:
b1=6/q^2(1+q) = 6/(4*3)=6/12=0.5
b7=b1q^6=0.5*64=32
2) q=0.5:
b1=6/q^2(1+q)=6/(0.25*1.5)=24/1.5=48/3=16
b7=b1q^6=16*2^(-6)=2^4*2^(-6)=2^-2=0.25
ответ: 32; 0.25
4) bn=3^(n-1)
b1=3^0=1
b2=3^1=3
q=b2/b1=3/1=3
S4=b1*(q^4-1)/(q-1)=1*(81-1)/(3-1)=80/2=40
а) (с+2)(с-3)-(с+1)(с+3) = (c^2 + 2c - 3c - 6) - (c^2 + c + 3c + 3)=
= c^2 - c - 6 - ( c^2 + 4c + 3) = c^2 - c - 6 - c^2 - 4c - 3 = 3 - 5c.
б) (р+3)(р-11)+(р+6)^2 = (p^2 + 3p - 11p - 33) + (p^2 + 12p + 36) = p^2 - 8p - 33 + p^2 + 12p + 36 = 2p^2 + 4p + 3.
в) (4х-3)^2+6х(4-х) = 16x^2 - 24x + 9 + 24x - 6x^2 = 10x^2 + 9.
г) (b+3)(b-3)+(2b+3)^2 = b^2 + 3b - 3b - 9 + 4b^2 + 12b + 9 = 5b^2 + 12b.
д) (а-5)(а+1)-(а-6)(а-1) = a^2 - 5a + a - 5 - (a^2 - 6a - a + 6) = a^2 - 4a - 5 - (a^2 - 7a + 6) = a^2 - 4a - 5 - a^2 + 7a - 6 = 3a - 11.
е) (a-4)(a+4)-2a(3-a) = a^2 - 4a + 4a - 16 - 6a + 2a^2 = 3a^2 - 6a - 16.