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\(A=\frac{4}{5.7}+\frac{4}{7.9}+...+\frac{4}{69.71}\)
\(A=4\left(\frac{1}{5.7}+\frac{1}{7.9}+...+\frac{1}{69.71}\right)\)
\(A=\frac{4}{2}\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{69}-\frac{1}{71}\right)\)
\(A=2\left(\frac{1}{5}-\frac{1}{71}\right)\)
\(A=2.\frac{66}{355}=\frac{132}{355}\)
a) Dấu hiệu là điểm bài kiểm tra môn Toán HKI của mỗi em học sinh lớp 7A
b)
c) _
X = \(\dfrac{2.2+4.5+5.4+6.7+7.6+8.5+9.2+10}{32}\)= 6,125
Mốt = Mo = 6
d)
\(\left(-\dfrac{1}{2}\right)-\left(-\dfrac{3}{5}\right)+9-\dfrac{1}{9}+\dfrac{1}{71}-\left(-\dfrac{2}{7}\right)+\dfrac{4}{35}-\dfrac{7}{18}\)
\(=\left(-\dfrac{22635}{44730}\right)-\left(-\dfrac{26838}{44730}\right)+\dfrac{402570}{44730}-\dfrac{4970}{44730}+\dfrac{630}{44730}-\left(-\dfrac{12780}{44730}\right)+\dfrac{5112}{44730}-\dfrac{35784}{44730}\)
\(=\left(-\dfrac{22635}{44730}\right)+\dfrac{26838}{44730}+\dfrac{402570}{44730}-\dfrac{4970}{44730}+\dfrac{630}{44730}+\dfrac{12780}{44730}+\dfrac{5112}{44730}-\dfrac{35784}{44730}\)
\(=\dfrac{-22635+26838+402570-4970+630+12780+5512-35784}{44730}\)
\(=\dfrac{384941}{44730}\)
a) -1/24 - [ 1/4 - ( 1/2 - 7/8 )]
= -1/24 - [ 1/4 +3/8 ]
= -1/24 - 5/8
= -2/3.
a) -1/24 - [ 1/4 - ( 1/2 - 7/8 )]
= -1/24 - [ 1/4 +3/8 ]
= -1/24 - 5/8
= -2/3.
\(=\dfrac{-1}{2}+\dfrac{3}{5}-\dfrac{1}{9}+\dfrac{1}{71}+\dfrac{2}{7}+\dfrac{4}{35}-\dfrac{7}{18}\)
\(=\left(-\dfrac{1}{2}-\dfrac{1}{9}-\dfrac{7}{18}\right)+\left(\dfrac{3}{5}+\dfrac{2}{7}+\dfrac{4}{35}\right)+\dfrac{1}{71}\)
=1/71
Gọi biểu thức trên là A
A : 4 = 1/5.7 + 1/7.9 + ... + 1/69.71
A : 4 = 1/5 - 1/7 + 1/7 - 1/9 + .... + 1/69 - 1/71
A : 4 = 1/5 - 1/71
A : 4 = 66/355
A = 66/355 . 4
A = 264/355