Câu 18. Thực hiện phép tính: (-8).(-8).(-8).(-8) – 84 + 105.
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1) 5 + (-4) = 1
2) (-8) + 2 = -6
3) 8 + (-2) = 6
4) 11 + (-3) = 8
5) (-11) + 2 = -9
6) (-7) + 3 = -4
7) (-5) + 5 = 0
8) 11 + (-12) = -1
9) (-18) + 20 = 2
10) (15) + (-12) = 3
11) (-17) + 17 = 0
12) 16 + (-2) = 14
13) (30) + (-14) = 16
14) (-19) + 20 = 1
15) (-18) + 15 = -3
16) (10) + (-6) = 4
17) (-28) + 14 = -14
18) 15 + (-30) = -15
19) (15) + (-4) = 11
20) (-21) + 11 = -10
21) 8 + (-22) = -14
22) (-15) + 4 = -11
23) (-3) + 2 = -1
24) 17 + (-14) = 3
25) 17 + (-14) = 3
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a)
160 : (4 × 8) = 160 : 32 = 5
160 : 4 : 8 = 40 : 8 = 5
Vậy 160 : (4 × 8) = 160 : 4 : 8.
96 : (3 × 8) = 96 : 24 = 4
96 : 3 : 8 = 32 : 8 = 4
Vậy 96 : (3 × 8) = 96 : 3 : 8.
105 : (5 × 7) = 105 : 35 = 3
105 : 5 : 7 = 21 : 7 = 3
Vậy 105 : (5 × 7) = 105 : 5 : 7.
Nhận xét: a : (b × c) = a : b : c
b)
270 : (9 × 6) = 270 : 9 : 6 = 30 : 6 = 5
420 : (7 × 3) = 420 : 7 : 3 = 60 : 3 = 20
144 : (2 × 8) = 144 : 2 : 8 = 72 : 8 = 9
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Dấu "^" của cậu nghĩa là phân số?
\(a,-1,75-\left(-\dfrac{1}{9}-2\dfrac{1}{18}\right)=-\dfrac{7}{4}-\left(-\dfrac{2}{18}-\dfrac{37}{18}\right)=-\dfrac{7}{4}+\dfrac{13}{6}=\dfrac{5}{12}\)
\(b,-\dfrac{1}{12}-\left(2\dfrac{5}{8}-\dfrac{1}{3}\right)=-\dfrac{1}{12}-\dfrac{55}{24}=-\dfrac{19}{8}\)
\(c,-\dfrac{5}{6}-\left(-\dfrac{3}{8}+\dfrac{1}{30}\right)=-\dfrac{5}{6}+\dfrac{41}{120}=-\dfrac{59}{120}\)
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a) \(18+25\times4-4^3\)
\(=18+100-64\)
\(=118-64\)
\(=54\)
b) \(275-\left(49+125\div5^3\right)\)
\(=275-\left(49+125\div125\right)\)
\(=275-\left(49+1\right)\)
\(=275-49-1\)
\(=226-1\)
\(=225\)
c) \(2015+\left(8\times15-\left(18-8\right)^2\right)\)
\(=2015+\left(8\times15-\left(10\right)^2\right)\)
\(=2015+\left(8\times15-100\right)\)
\(=2015+\left(120-100\right)\)
\(=2015+20\)
\(=2035\)
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bài 1:
a: Ta có: \(2\sqrt{18}-9\sqrt{50}+3\sqrt{8}\)
\(=6\sqrt{2}-45\sqrt{2}+6\sqrt{2}\)
\(=-33\sqrt{2}\)
b: Ta có: \(\left(\sqrt{7}-\sqrt{3}\right)^2+7\sqrt{84}\)
\(=10-2\sqrt{21}+14\sqrt{21}\)
\(=12\sqrt{21}+10\)
Bài 2:
a: Ta có: \(\sqrt{\left(2x+3\right)^2}=8\)
\(\Leftrightarrow\left|2x+3\right|=8\)
\(\Leftrightarrow\left[{}\begin{matrix}2x+3=8\\2x+3=-8\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{5}{2}\\x=-\dfrac{11}{2}\end{matrix}\right.\)
b: Ta có: \(\sqrt{9x}-7\sqrt{x}=8-6\sqrt{x}\)
\(\Leftrightarrow4\sqrt{x}=8\)
hay x=4
c: Ta có: \(\sqrt{9x-9}+1=13\)
\(\Leftrightarrow3\sqrt{x-1}=12\)
\(\Leftrightarrow x-1=16\)
hay x=17
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a) \(\frac{3}{4}+\left(\frac{-1}{3}\right)-\frac{5}{18}=\frac{5}{36}\)
b) \(-2+\left(\frac{-5}{8}\right)+\frac{3}{4}=\frac{-15}{8}\)
c) \(\frac{15}{8}.\frac{12}{5}-\frac{11}{3}=\frac{5}{6}\)
d) \(\frac{6}{7}+\frac{5}{7}:5-\frac{8}{9}=\frac{1}{9}\)
mk chỉ đưa ra kp thôi!
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