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19x64-76x34=-1368
136x68+16x272=13600
ung ho nha
a) = 35 x 12 + 65 x 12 + 65 = (35 + 65) x 12+ 65 = 100 x 12 + 65 = 1200 + 65 = 1265
b) tuong tu a
b) (2 + 4 + 6 + ...+ 100) x ( 36 x 3 x 111 - 36 x 3 x 111) = (2 + 4 + 6 + ...+ 100) x 0 = 0
a, 19 x 64 + 76 x 34
= 19 x 2 x 32 + 38 x 2 x 34
= 38 x 32 + 38 x 68
= 38 x ( 32 + 68 )
= 38 x 100
= 3800
b, 35 x 12 + 65 x 13
= 35 x 12 + 65 x 12 + 65
= ( 35 + 65 ) x 12 + 65
= 100 x 12 + 65
= 1200 + 65
= 1265
d, ( 2 + 4 + 6 + ... + 1000) x ( 36 x 333 - 108 x 111 )
= ( 2 + 4 + 6 + ... + 1000 ) x ( 36 x 3 x 111 - 108 x 111)
= ( 2 + 4 + 6 + ...+ 1000 ) x ( 108 x 111 - 108 x 111 )
= ( 2 + 4 + 6 + ... + 1000 ) x 0
= 0
Câu c chịu
a, 136x68 + 16x2x136 = 136x68+ 32x136 = 136x(68+32) = 136x100 = 13600
b,37 - 11x3x(24-23)+22x10 = 37 - 33x1 +220 = 224
Tích đúng cho mk nhá ^^
Đặt \(A=\frac{1}{3}+\frac{1}{3^2}+\frac{1}{3^3}+...+\frac{1}{3^8}\)
\(\Leftrightarrow\)\(3A=1+\frac{1}{3}+\frac{1}{3^2}+...+\frac{1}{3^7}\)
\(\Leftrightarrow\)\(3A-A=\left(1+\frac{1}{3}+\frac{1}{3^2}+...+\frac{1}{3^7}\right)-\left(\frac{1}{3}+\frac{1}{3^2}+\frac{1}{3^3}+...+\frac{1}{3^8}\right)\)
\(\Leftrightarrow\)\(2A=1-\frac{1}{3^8}\)
\(\Leftrightarrow\)\(2A=\frac{3^8-1}{3^8}\)
\(\Leftrightarrow\)\(A=\frac{3^8-1}{3^8}:2\)
\(\Leftrightarrow\)\(A=\frac{3^8-1}{3^8}.\frac{1}{2}\)
\(\Leftrightarrow\)\(A=\frac{3^8-1}{2.3^8}\)
b) Đặt \(A=\frac{1}{3}+\frac{1}{3^2}+\frac{1}{3^3}+.....+\frac{1}{3^8}\)
\(\Rightarrow\)\(3A=1+\frac{1}{3}+\frac{1}{3^2}+....+\frac{1}{3^7}\)
\(\Rightarrow\)\(3A-A=\left(1+\frac{1}{3}+\frac{1}{3^2}+...+\frac{1}{3^7}\right)-\left(\frac{1}{3}+\frac{1}{3^2}+\frac{1}{3^3}+....+\frac{1}{3^8}\right)\)
\(\Rightarrow\)\(2A=1-\frac{1}{3^8}\)
\(\Rightarrow\)\(A=\frac{1-\frac{1}{3^8}}{2}\)
\(135\cdot68+16\cdot272\)
\(=\) \(135\cdot68+16\cdot4\cdot68\)
\(=\) \(135\cdot68+64\cdot68\)
\(=\) \(68\cdot\left(135+64\right)\)
\(=\) \(68\cdot199\)
\(=\) \(13532\)
136x68+16x272=136x68+16x136x2=136x(68+16x2)=136x(68+32)=136x100=13600