Tính bằng cách hợp lí nhất
(2^2 + 2^1 + 2^2 + 2^3). 2^0. 2^1. 2^2. 2^3
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z lm lại, nhưng nó cứ sao ý!
\(\left(2^2+2^1+2^2+2^3\right).2^0.2^1.2^2.2^3\)
\(=18.64\)
\(=1152\)
Sửa đề:
đặt A = \(\left(2^0+2^1+2^2+2^3\right).2^0.2^1.2^2.2^3\)
\(A=\left(1+2+2^2+2^3\right).2^6\)
\(A=2^6+2^7+2^8+2^9\)
\(\Rightarrow2A=2^7+2^8+2^9+2^{10}\)
\(\Rightarrow2A-A=2^{10}-2^6\)
\(A=2^{10}-2^6\)
\(A=960\)
xem đề mk ghi như z cs đúng ko?
(2^2 + 2^1 + 2^2 + 2^3). 2^0. 2^1. 2^2. 2^3
=(4 + 2 + 4 + 8). 1. 2. 4. 8
=18.64
=1152
a) 21x72-11x72+90x72+49x125x16
= 21 x 49 - 11 x 49 + 90 x 49 + 49 x 125 x 16
= 49 x ( 21 - 11 + 90 + 125 x 16 )
= 49 x ( 21 - 11 + 90 + 2000 )
= 49 x 2100
= ( 50 - 1 ) x 2100
= 50 x 2100 - 2100
= 105 000 - 2100
= 102 900
\(a,1\dfrac{4}{7}.3\dfrac{4}{11}.3\dfrac{11}{15}.5\dfrac{5}{8}\)
\(=\dfrac{11}{7}.\dfrac{27}{11}.\dfrac{56}{15}.\dfrac{45}{8}\)
\(=\dfrac{11.27.56.45}{7.11.15.8}\)
\(=\dfrac{1.3.7.3}{1.1.1.1}\)
\(=63\)
\(b,\dfrac{3}{4}.1\dfrac{1}{2}+\dfrac{3}{4}.\dfrac{1}{2}\)
\(=\dfrac{3}{4}.\left(1\dfrac{1}{2}+\dfrac{1}{2}\right)\)
\(=\dfrac{3}{4}.2\)
\(=\dfrac{3}{2}\)
S=\(3\left(1+\frac{1}{1+2}+\frac{1}{1+2+3}+...+\frac{1}{1+2+3+...+100}\right)\)
\(S=3\left(1+\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{1}{5050}\right)\)
\(S=3.\frac{1}{2}\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{10100}\right)\)
\(S=\frac{3}{2}\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{100.101}\right)\)
\(S=\frac{3}{2}\left(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{100}-\frac{1}{101}\right)\)
\(S=\frac{3}{2}\left(1-\frac{1}{101}\right)\)
\(S=\frac{3}{2}.\frac{100}{101}=\frac{150}{101}\)
\(\left(2^2+2^1+2^2+2^3\right).2^0.2^1.2^2.2^3\)
\(\Leftrightarrow\left(2^2+2^1+2^2+2^3\right).2^0.2^{1+2+3}\)
\(\Leftrightarrow\left(2^2+2^1+2^2+2^3\right).2^0.2^6\)
\(\Leftrightarrow2304^o\)
Ps; k nhớ
# Aeri #
Thử cách này xem?
\(\left(2^2+2^1+2^2+2^3\right).2^0.2^1.2^2.2^3.\)
\(\Leftrightarrow\left(2+2+4+8\right).1.2.4.8\)
\(\Leftrightarrow18.64\)
\(\Leftrightarrow1152\)
Ps ; thấy cái nào hợp lý thì chọn nhé , nhớ k
# Aeri #