D=4+4^2+...+4^n

=>\(4\cdot D=4^2+4^3+...+4^{n+1}\)

=>\(3D=4^{n+1}+4^n+...+4^3+4^2-4^n-...-4^2-4\)

=>\(3D=4^{n+1}-4\)

=>\(D=\dfrac{4^{n+1}-4}{3}\)

-58.(-42) + 42.12 

= 58.42 + 42.12

= 42.(58+12)

= 42.70

= 2940

a) (2¹⁷+ 17²).(9¹⁵– 3¹⁵).(2⁴ – 4²)

= (2¹⁷ + 17²).(9¹⁵ – 3¹⁵).(16 - 16)

= 0

Vậy giá trị cần tìm là: 0

b) (8²⁰¹⁷– 8²⁰¹⁵) : (8²¹⁰⁴.8)

= 8²⁰¹⁵.(8²- 1) : 8²⁰¹⁵ 

= 64 – 1

= 63

Vậy giá trị cần tìm là: 63

a) (217 + 172).(915 – 315).(24 – 42)

= (217 + 172).(915 – 315).(16 - 16)

= 0

Vậy giá trị cần tìm là: 0

b) (82017 – 82015) : (82104.8)

= 82015.(82- 1) : 82015 

= 64 – 1

= 63

Vậy giá trị cần tìm là: 63

a) 0

b) 63

\(\left(2^{17}+7^2\right).\left(9^{15}-3^{15}\right).\left(2^4-4^2\right)\)

\(=\left(2^{17}+7^2\right).\left(9^{15}-3^{15}\right).\left(16-16\right)\)

\(=\left(2^{17}+7^2\right).\left(9^{15}-3^{15}\right).0\)

\(=0\)

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\(\left(7^{1997}-7^{1995}\right):\left(7^{1994}.7\right)\)

\(=\left[7^{1995}\left(7^2-1\right)\right]:7^{1995}\)

\(=7^{1995}.48:7^{1995}\)

\(=48\)

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\(\left(1^2+2^3+3^4+4^5\right).\left(1^3+2^3+3^3+4^3\right).\left(3^8-81^2\right)\)

\(=\left(1^2+2^3+3^4+4^5\right).\left(1^3+2^3+3^3+4^3\right).\left(6561-6561\right)\)

\(=\left(1^2+2^3+3^4+4^5\right).\left(1^3+2^3+3^3+4^3\right).0\)

\(=0\)

-------------------------------------------------

\(\left(2^8+8^3\right):\left(2^5.2^3\right)\)

\(=\left[2^8+\left(2^3\right)^3\right]:2^8\)

\(=\left(2^8+2^9\right):2^8\)

\(=2^8.\left(1+2\right):2^8\)

\(=2^8.3:2^8\)

\(=3\)

sos

7*9+14*27+21*63/21*27+42*48+63*108

=63+7*2*9*3+21*63/7*3*9*3+21*2*16*3+63*108

=63+63*6+21*63/63*9+63*32+63*108

=63*(1+6+21)/63*(9+32+108)

=1+6+21/9+32+108

=28/149

13 − 18 − − 42 − 15 = 13 − 18 + 42 − 15 = 13 + 42 + − 18 − 15 = 55 + − 33 = 22.

a,  2 17 + 17 2 9 15 - 3 15 2 4 - 4 2

=  2 17 + 17 2 9 15 - 3 15 16 - 16

=  2 17 + 17 2 9 15 - 3 15 . 0

= 0

b,  1 2 + 2 3 + 3 4 + 4 5 . ( 1 3 + 2 3 + 3 3 + 4 3 ) ( 3 8 - 81 2 )

=  1 2 + 2 3 + 3 4 + 4 5 . ( 1 3 + 2 3 + 3 3 + 4 3 ) ( 3 4 . 2 - 81 2 )

=  1 2 + 2 3 + 3 4 + 4 5 . ( 1 3 + 2 3 + 3 3 + 4 3 ) ( 81 2 - 81 2 )

=  1 2 + 2 3 + 3 4 + 4 5 . ( 1 3 + 2 3 + 3 3 + 4 3 ) . 0

= 0

c,  7 24 + 7 23 : 7 22

=  7 24 : 7 22 + 7 23 : 7 22

=  7 24 - 22 + 7 23 - 22

=  7 2 + 7 1

= 49 + 7 = 56

\(=\dfrac{9^3\cdot\left(2^3\cdot3+45\right)}{9^3}=8\cdot3+45=69\)

hợp lí nhất là tính trong ngoặc trước:)