Tính nhanh : 1/4+0,75+1/3+2/3+6+3+2017,2018 = ?
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1) 2,75 - 5/6 × 2/5 = 2,75 - (5/6) × (2/5) = 2,75 - 1/3 = 2,75 - 0,33 = 2,42
2) 1,25 - (5/6 - 0,75) - 3/5 = 1,25 - (5/6 - 0,75) - 3/5 = 1,25 - (5/6 - 3/4) - 3/5 = 1,25 - (5/6 - 9/12) - 3/5 = 1,25 - (10/12 - 9/12) - 3/5 = 1,25 - 1/12 - 3/5 = 1,25 - 0,08 - 0,6 = 1,25 - 0,68 = 0,57
3) 4/9 × 0,75 + 8/5 + 3,125 = (4/9) × 0,75 + 8/5 + 3,125 = 0,44 + 8/5 + 3,125 = 0,44 + 1,6 + 3,125 = 0,44 + 4,725 = 5,165
4) 1,125 - 4/7 - 0,12 = 1,125 - (4/7) - 0,12 = 1,125 - 0,57 - 0,12 = 0,435 - 0,12 = 0,315
5) (1/3 + 0,4) × 3,5 + (1/6 + 0,75) × 6/5
A = \(\dfrac{1}{2}\) - 0,75 + \(\dfrac{5}{4}\) - \(\dfrac{6}{12}\)
A = 0,5 - 0,75 + 1,25 - 0,5
A = (0,5 - 0,5) + (1,25 - 0,75)
A = 0,5
B = (-\(\dfrac{1}{7}\))0 - 22.(\(\dfrac{2}{3}\))2
B = 1 - 22. \(\dfrac{4}{9}\)
B = 1 - \(\dfrac{88}{9}\)
B = - \(\dfrac{79}{9}\)
a)\(=\frac{2017}{2016}.\frac{3}{4}-\frac{1}{2016}.\frac{3}{4}\)
\(=\frac{3}{4}\left(\frac{2017}{2016}-\frac{1}{2016}\right)\)
\(=\frac{3}{4}.1\)
\(=\frac{3}{4}\)
b)\(=\frac{2015}{2016}\left(\frac{1}{2}+\frac{1}{3}-\frac{5}{6}\right)\)
\(=\frac{2015}{2016}.0\)
\(=0\)
Bài 2:
a: \(\left(3x-3\right)^2-\left(5x-3\right)^2=0\)
\(\Leftrightarrow\left(3x-3-5x+3\right)\left(3x-3+5x-3\right)=0\)
\(\Leftrightarrow-2x\left(8x-6\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{3}{4}\end{matrix}\right.\)
Tính nhanh:
3/4 : 0,75 + 50% : 1/2 + 4/5 x 1 1/4
= 0,75 : 0,75 + 1/2 : 1/2 + 4/5 x 5/4
= 1 + 1 + 1
= 3
\(=\frac{3}{4}:\frac{3}{4}+\frac{1}{2}:\frac{1}{2}+\frac{4}{5}.\frac{5}{4}\)
\(=1+1+1\)
\(=3\)
Chúc bạn học tốt
\(\text{A=}\left(\dfrac{7}{8}-0,25\right):\left(\dfrac{5}{6}-0,75\right)^2\)
\(A=\left(\dfrac{7}{8}-\dfrac{1}{4}\right):\left(\dfrac{5}{6}-\dfrac{3}{4}\right)^2\)
\(A=\left(\dfrac{7}{8}+\dfrac{-1}{4}\right):\dfrac{1}{144}\)
\(A=\dfrac{5}{8}.144=90\)
\(\text{B=}\dfrac{3}{4}.1\dfrac{4}{9}-\left(\dfrac{-3}{4}\right)\)
\(B=\dfrac{3}{4}.\dfrac{13}{9}+\dfrac{3}{4}\)
\(B=\dfrac{13}{12}+\dfrac{3}{4}\)
\(B=\dfrac{11}{6}\)
= 2028,2018