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(3.5)^2-(16x2)^2=3^2x5^2-16^2x2^2=9x25-256x4=225-1024=-799
(39.42-37.42):42=[42.(39-37)]:42=42x2:42=1x2=2
2448:[190-(23-6)]=2448:[190-17)=2448:173=2448/173 nha Dương Ngọc Phuong Linh
a) \(3^6:3^2+2^3.2^2=3^4+2^5=81+32=113\)
b)\(\left(39.42-37.42\right):42=\left(39-37\right)42:42=2.\left(42:42\right)=2.1=2\)
3^6:3^2+2^3.2^2.(39.42-37.42):42
=3^4+2^5.42.(39-37):42
=81-32.2
=81-6=17
a, 20^2 - 6^ 2= 400 - 36 = 364
b,3^3 . 18 - 3^3 . 12 = 3^3 . ( 18-12) = 27 . 6 = 162
c, 39 . 213 + 87 . 39 = ( 213 + 87) . 39 = 300 . 39 = 110700
d, 80 - [ 130 - ( 12 - 4)^2] = 80 - [130 - (3^2) ] = 80 - 130 - 9 = -59
\(\Rightarrow2S=6+\frac{3}{1}+\frac{3}{2}+...+\frac{3}{2^8}\)
\(\Rightarrow2S-S=\left(6+3+\frac{3}{2}+...+\frac{3}{2^8}\right)-\left(3+\frac{3}{2}+...+\frac{3}{2^9}\right)\)
\(\Rightarrow S=3-\frac{3}{2^9}\)
\(S=3+\frac{3}{2}+\frac{3}{2^2}+\frac{3}{2^3}+...+\frac{3}{2^9}\)
\(\Rightarrow\frac{1}{2}.S=\frac{3}{2}+\frac{3}{2^2}+\frac{3}{2^3}+...+\frac{3}{2^{10}}\)
\(\Rightarrow S-\frac{1}{2}.S=\frac{1}{2}.S=3+\frac{3}{2}+\frac{3}{2^2}+\frac{3}{2^3}+...+\frac{3}{2^9}-\left(\frac{3}{2}+\frac{3}{2^2}+\frac{3}{2^3}+...+\frac{3}{2^{10}}\right)\)
\(\Rightarrow\frac{1}{2}.S=3-\frac{3}{2^{10}}\)
\(\Rightarrow S=6-\frac{6}{2^{10}}\)
a. 3^6 : 3^2 + 2^3 . 2^ 2 = 3^ (6-3) + 2^(3+2) = 3^3 + 2^5= 27 + 32 =59
b. ( 39. 42 - 37.42) : 42 = [ 42. ( 39-37) ] :42 = 39 -37 = 2
a) 59
b) 2