tính nhanh

a, (756 - 217) - ( 183 -44)

\(=756-217-183+44\)

\(=\left(756+44\right)+\left(-217-183\right)\)

\(=800-400\)

\(=400\)

b, 11-12+13-14+15-16+17-18+19-20

\(=\left(11+19\right)-\left(12+18\right)+\left(13+17\right)-\left(14+16\right)+\left(15-20\right)\)

\(=30-30+30-30-5\)

\(=-5\)

a) \(\left(756-217\right)-\left(183-44\right)\)

= \(756-217-183+44\)

= \(\left(756+44\right)+\left(-217-183\right)\)

= \(800+\left(-400\right)\)

= \(400\)

trả lời giúp mình với

a) A = 83 x 74 + 0,01 x 7400 + 32 x 37

       = 83 x 74 + 74  + 16 x 2 x 37

       = 83 x 74 + 74 + 16 x 74

       = 74 x (83 + 1 + 16)

       = 74 x 100

       = 7400

a) \(9^8=\left(3^2\right)^8=3^{16}\)

\(27^3=\left(3^3\right)^3=3^9\)

\(81^2=\left(3^4\right)^2=3^8\)

\(\Leftrightarrow3^{16}:\left(3^9.3^8\right)\)

\(\Leftrightarrow3^{16}:3^{17}\)

\(\Leftrightarrow3^{-1}=\frac{1}{3}\)

a) 9^́́́8 : ̣(27³ . 81²)= 3^{16  :} 3⁹ . 3⁸ = 3¹⁵

\(5^2.n-3-2.5^2=5^2.3\)

\(\Rightarrow25n-3-2.25=25.3\)

\(\Rightarrow25.n-3-50=75\)

\(\Rightarrow25.n-53=75\)

\(\Rightarrow25.n=128\)

\(\Rightarrow n=\frac{128}{25}\)

\(5^2.n-3-2.5^2=5^2.3\)

\(\Rightarrow5^2.\left(n-2\right)-3=5^2.3\)

\(\Rightarrow\left(n-2\right)-3=3\)

\(\Rightarrow n-2=3+3\)

\(\Rightarrow n-2=6\)

\(\Rightarrow n=6+2\)

\(\Rightarrow n=8\)

a, \(2A=2+2^2+2^3+...+2^{2011}\)

\(2A-A=\left(2+2^2+2^3+...+2^{2011}\right)-\left(2^0+2^1+2^2+...+2^{2010}\right)\)

\(A=2^{2011}-1\)

b, \(4C=4^2+4^3+...+4^{n+1}\)

\(4C-C=\left(4^2+4^3+...+4^{n+1}\right)-\left(4+4^2+...+4^n\right)\)

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

\(C=\frac{4^{n+1}-4}{3}\)

a) A = 1 + 2 + 2² + ... + 2²⁰¹⁰

=> 2A = 2 + 2² + 2³ + ... + 2²⁰¹¹

Lấy 2A - A = (2 + 2² + 2³ + ... + 2²⁰¹¹) - (1 + 2 + 2² + ... + 2²⁰¹⁰)

              A = 2 + 2² + 2³ + ... + 2²⁰¹¹ - 1 - 2 - 2² - ... - 2²⁰¹⁰

                 = 2²⁰¹¹ - 1

b) C = 4 + 4² + 4³ +... + 4ⁿ

=> 4C = 4² + 4³ + 4⁴ + ... + 4^{n + 1}

Lấy 4C - C = (4² + 4³ + 4⁴ + ... + 4^{n + 1}) - ( 4 + 4² + 4³ +... + 4ⁿ)

            3C  = 4^{n + 1} - 4

              C  =(4^{n + 1} - 4) : 3

là sao vậy ak

ko rõ lắm 

B=1/25.27+1/27.29+1/29.31+.......+1/73.75

=1/25+1/75

=3/75+1/75

=4/75.

#)Giải :

\(B=\frac{1}{25.27}+\frac{1}{27.29}+...+\frac{1}{73.75}\)

\(2B=\frac{2}{25.27}+\frac{2}{27.29}+...+\frac{2}{73.75}\)

\(2B=\frac{1}{25}-\frac{1}{27}+\frac{1}{27}-\frac{1}{29}+...+\frac{1}{73}-\frac{1}{75}\)

\(2B=\frac{1}{25}-\frac{1}{75}\)

\(2B=\frac{2}{75}\)

\(B=\frac{2}{75}\div2\)

\(B=\frac{1}{75}\)

mình biết làm câu D thôi còn câu còn lại chắc bạn ghi sai đề

\(D=\frac{4^7.2^8}{3.2^{15}.16^2-5.2^2.\left(2^{10}\right)^2}=\frac{2^{14}.2^8}{3.2^{15}.\left(2^4\right)^2-5.2^2.2^{20}}=\frac{2^{22}}{3.2^{15}.2^8-5.2^22^{20}}=\frac{2^{22}}{3.2^{22}.2-5.2^{22}}\)

\(=\frac{2^{22}}{2^{22}\left(3.2-5\right)}=\frac{2^{22}}{2^{22}.1}=1\) bạn ơi dấu . là nhân nhé

1, CÓ( X+1,5)⁸ VÀ (2,7 -Y)¹²> HOẶC = 0

         MÀ (X+1,5)⁸ + (2,7-Y)¹²  =0

    SUY RA   \(\hept{\begin{cases}X+1,5=0\\2,7-Y=0\end{cases}}\)

      SUY RA\(\hept{\begin{cases}X=-1,5\\Y=2,7\end{cases}}\)

de ghe de cho nam ngaN

bạn ko làm thì thôi , ko cần bạn nói vậy