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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 6: b1: tìm x a) (x-5)^4=4 ² b) 2^2x.2^x=1024 c)2^x+3=2^x=9.64 d) (19x+25 ²):14=(13-8) ²-4 ² b2:tính tổn

Tháng Tám 3, 2022 Toán học 1 Comment 0 views

Toán Lớp 6: b1: tìm x
a) (x-5)^4=4 ² b) 2^2x.2^x=1024 c)2^x+3=2^x=9.64 d) (19x+25 ²):14=(13-8) ²-4 ²
b2:tính tổng
a)A=1+4+4²+4³+4^4+…+4^100
b)B=1-3+3²-3³+…+3^1000

Comments ( 1 )

  1. buithaianh98
    buithaianh98
    3 Tháng Tám, 2022 at 5:17 chiều
    Reply
    ~Bạn tham khảo~
    Bài 1:
    a)(x-5)^4 = 4^2
    =>(x-5)^4 =(2^2 )^2
    =>(x-5)^4 = 2^4
    =>x-5=2
    =>x=7
    Vậy x=7
    b)2^(2x).2^x =1024
    =>2^(3x)=1024
    =>2^(3x) = 2^10
    =>3x=10
    =>x=10/3
    Vậy x=10/3
    c) Sửa đề : 2^(x+3) + 2^x = 9.64
    =>2^x . 8+2^x = 576
    =>2^x (8+1) =576
    =>2^x . 9=576
    =>2^x =64
    =>2^x = 2^6
    =>x=6
    Vậy x-6
    d)(19x +25^2 ) : 14=(13-8)^2 -4^2
    =>(19x+ 625):14 = 5^2 – 16
    =>(19x+625):14=25-16
    =>(19x+625):14=9
    =>19x+625=126
    =>19x=126-625
    =>19x=-499
    =>x=(-499)/19
    Vậy x=(-499)/19
    Bài 2 :
    a)A=1+4+4^2 + 4^3 + 4^4 + … + 4^100
    =>4A=4+4^2 + 4^3 + 4^4 +4^5 + … + 4^101
    =>4A-A=(4+4^2 + 4^3 + 4^4 +4^5 + … + 4^101 )-(1+4+4^2 + 4^3 + 4^4 + … + 4^100 )
    =>3A=4^101 -1
    =>A=(4^101 -1)/3
    b) Sửa đề : B=1+3+3^2+3^3 +…+3^1000
    =>3B=3+3^2+3^3 +3^4 +…+3^1001
    =>3B-B = ( 3+3^2+3^3 +3^4 +…+3^1001 )-(1+3+3^2+3^3 +…+3^1000)
    =>3B=3^1001 – 1
    =>B=(3^1001 – 1)/3

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222-9+11+12:2*14+14 = ? ( )

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