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a) \(\frac{8}{21}+\frac{13}{21}=\frac{8+13}{21}=\frac{21}{21}=1\)
b) \(\frac{5}{6}:\frac{-7}{12}=\frac{5}{6}.\frac{12}{-7}=\frac{10}{-7}\)
c) \(-4\frac{1}{4}-\frac{3}{4}=\frac{-17}{4}-\frac{3}{4}=\frac{-17-3}{4}=\frac{-20}{4}=-5\)
d) \(\frac{7}{9}.\frac{8}{17}+\frac{7}{9}.\frac{15}{17}-\frac{7}{9}.\frac{6}{17}\)
\(=\frac{7}{9}.\left(\frac{8}{17}+\frac{15}{17}-\frac{6}{17}\right)\)
\(=\frac{7}{9}.\frac{17}{17}\)
\(=\frac{7}{9}.1\)
\(=\frac{7}{9}\)
a) \(\frac{8}{21}+\frac{13}{21}=1\)
b) \(\frac{5}{6}\div\frac{-7}{12}=\frac{5}{6}.\frac{-12}{7}=\frac{-10}{7}\)
c) \(-4\frac{1}{4}-\frac{3}{4}=\frac{-17}{4}-\frac{3}{4}=-5\)
d) \(\frac{7}{9}.\frac{8}{17}+\frac{7}{9}.\frac{15}{7}-\frac{7}{9}.\frac{6}{17}=\frac{7}{9}.\left(\frac{8}{17}+\frac{15}{17}-\frac{6}{17}\right)=\frac{7}{9}.1=\frac{7}{9}\)
a,để sắp sếp thì ta nên quy đồng cho về chung mẫu :13/21=221/357,152/17=3192/357,13/17=273/357,5/21=85/357
như thế ta sắp sếp theo thứ tự:152/17,13/17,13/21,5/21
câu b cách làm như câu a
cái này mình không chắc đâu bạn đi hỏi người khác để chắc chắn hơn đi
Bài 1:
a; \(\dfrac{5}{18}\) + \(\dfrac{8}{19}\) - \(\dfrac{7}{21}\) + (- \(\dfrac{10}{36}\) + \(\dfrac{11}{19}\) + \(\dfrac{1}{3}\)) - \(\dfrac{5}{8}\)
= \(\dfrac{5}{18}\) + \(\dfrac{8}{19}\) - \(\dfrac{1}{3}\) -\(\dfrac{10}{36}\) + \(\dfrac{11}{19}\) + \(\dfrac{1}{3}\) - \(\dfrac{5}{8}\)
= (\(\dfrac{5}{18}\) - \(\dfrac{10}{36}\)) + (\(\dfrac{8}{19}\) + \(\dfrac{11}{19}\)) - (\(\dfrac{1}{3}\) - \(\dfrac{1}{3}\)) - \(\dfrac{5}{8}\)
= (\(\dfrac{5}{18}\) - \(\dfrac{5}{18}\)) + \(\dfrac{19}{19}\) - 0 - \(\dfrac{5}{8}\)
= 0 + 1 - \(\dfrac{5}{8}\)
= \(\dfrac{3}{8}\)
b; \(\dfrac{1}{13}\) + (\(\dfrac{-5}{18}\) - \(\dfrac{1}{13}\) + \(\dfrac{12}{17}\)) - (\(\dfrac{12}{17}\) - \(\dfrac{5}{18}\) + \(\dfrac{7}{5}\))
= \(\dfrac{1}{13}\) - \(\dfrac{5}{18}\) - \(\dfrac{1}{13}\) + \(\dfrac{12}{17}\) - \(\dfrac{12}{17}\) + \(\dfrac{5}{18}\) - \(\dfrac{7}{5}\)
= (\(\dfrac{1}{13}\) - \(\dfrac{1}{13}\)) + (\(\dfrac{12}{17}\) - \(\dfrac{12}{17}\)) + (-\(\dfrac{5}{18}\) + \(\dfrac{5}{18}\)) - \(\dfrac{7}{5}\)
= 0 + 0 + 0 - \(\dfrac{7}{5}\)
= - \(\dfrac{7}{5}\)
Bài 1 c;
\(\dfrac{15}{14}\) - (\(\dfrac{17}{23}\) - \(\dfrac{80}{87}\) + \(\dfrac{5}{4}\)) + (\(\dfrac{17}{23}\) - \(\dfrac{15}{14}\) + \(\dfrac{1}{4}\))
= \(\dfrac{15}{14}\) - \(\dfrac{17}{23}\) + \(\dfrac{80}{87}\) - \(\dfrac{5}{4}\) + \(\dfrac{17}{23}\) - \(\dfrac{15}{14}\) + \(\dfrac{1}{4}\)
= (\(\dfrac{15}{14}-\dfrac{15}{14}\)) + (\(-\dfrac{17}{23}+\dfrac{17}{23}\)) - (\(\dfrac{5}{4}\) - \(\dfrac{1}{4}\)) + \(\dfrac{80}{87}\)
= 0 + 0 - 1 + \(\dfrac{80}{87}\)
= - \(\dfrac{7}{87}\)
Đề trên lỗi nhé ae , đề đúng đây:
1. Tìm số đối của mỗi số nguyên sau: -7; 0; -4; 12; |-5|
và |5|.
2. Tính:
a) 8274 + 226 ;
b) (- 5 ) + ( -11) ; c) (- 43) + (-9)
3. Tính:
a) 17 + ( - 7) ;
b) (-96) + 64 ;
c) 75 + ( -325)
4. Tính:
a) 10- (-3) ;
b) (-21) – (-19);
c) 13 – 30 ;
d) 9 – (- 9)
5. Tính tổng:
a) (-30) + 15 + 10 + ( -15) ;
b) 17 + ( -12) + 25 – 17 ; b) 17 + ( -12) + 25 – 17 ;
c) (-14) + 250 + ( - 16) + (- 250) ;
d) ( -3) + ( - 14) + 27 + ( -10)
1. số đối: -7; 0; -4; 12; \(|-5|\); 5
là: 7; 0; 4; -12; -5; -5
2,3,4,a, 8274 + 226 = 8500
b, -5 + -11 = -16
c, -43 + -9 = -52
d, 17 + -7 = 10
e, -96 + 64 = -32
f, 75 + -325 = -250
g, 10 - (-3) = 10 + 3 = 13
h, -21 + 19 = -2
.., 13 - 30 = -17
.., 9 + 9 = 18
5, a,
-30 + 15 + 10 + -15 = -30 + 10 = 20
b, 17 + -12 + 25 - 17 = -12 + 25 = 13
c,-14 +250 - 16 - 250 = -14 + -16 = -30
d,-3 - 14 + 27 - 10 = 0
e, -14 + 250 - 16 - 250 = -14 + -16 = -30
f, -3 - 14 + 27 - 10 = 0
a; \(\dfrac{9}{4}\) - \(\dfrac{-11}{4}\)
= \(\dfrac{9}{4}\) + \(\dfrac{11}{4}\)
= \(\dfrac{20}{4}\)
= 5
b; \(\dfrac{7}{8}\) - \(\dfrac{3}{-8}\) - \(\dfrac{1}{8}\)
= \(\dfrac{7}{8}\) + \(\dfrac{3}{8}\) - \(\dfrac{1}{8}\)
= \(\dfrac{7+3-1}{8}\)
= \(\dfrac{9}{8}\)
c; \(\dfrac{-5}{21}\) - \(\dfrac{25}{21}\) - \(\dfrac{-1}{21}\)
= \(\dfrac{-5}{21}\) - \(\dfrac{25}{21}\) + \(\dfrac{1}{21}\)
= \(\dfrac{-5-25+1}{21}\)
= \(\dfrac{-29}{21}\)
hộ C1: Tìm x biết
a 2x-35=15
=>2x=15+35=50
=>x=25
b 3x+17=2
=>3x=2-17=-15
=>x=5
c x+3/15=1/3
x=1/3-3/15=2/15
d x-12/4=1/2
x=1/2+12/4=7/2
a. 2x-35=15
2x=15+35
2x=50
x=50:2
x=25
Vậy x=25
b. 3x+17=2
3x=2-17
3x=-15
x=-15:3
x=-5
Vậy x=-5
c. \(\frac{x+3}{15}=\frac{1}{3}\)
\(\Rightarrow3x+9=15\)
\(3x=15-9\)
\(3x=6\)
\(x=6:3\)
\(x=3\)
Vậy x=3
d. \(\frac{x-12}{4}=\frac{1}{2}\)
\(\Rightarrow2x-24=4\)
\(2x=4+24\)
\(2x=28\)
\(x=28:2\)
\(x=14\)
Vậy x=14
\(A=98.42-\left\{50.\left[\left(18-2^3\right):2+3^2\right]\right\}\)
\(=98.42-\left\{50.\left[\left(18-8\right):2+9\right]\right\}\)
\(=98.42-\left[50\left(10:2+9\right)\right]\)
\(=98.42-\left(50.14\right)\)
\(=4116-700=3416\)
\(B=-80-\left[-130-\left(12-4\right)^2\right]+2008^0\)
\(=-80-\left(-130-8^2\right)+1\)
\(=-80-\left(-130-64\right)+1\)
\(=-80+130+64+1\)
\(=115\)
\(C=1024:2^4+140:\left(38+2^5\right)-7^{23}:7^{21}\)
\(=1024:16+140:\left(38+32\right)-7^2\)
\(=64+140:70-49\)
\(=64+2-49=17\)
\(D=\left(2^{17}+15^4\right).\left(3^{19}-2^{17}\right).\left(2^4-4^2\right)\)
\(=\left(2^{17}+15^4\right).\left(3^{19}-2^{17}\right).\left(16-16\right)\)
\(=\left(2^{17}+15^4\right).\left(3^{19}-2^{17}\right).0\)
\(=0\)
\(E=100+98+96+....+4+2-97-95-....-3-1\)
\(=100+\left(98-97\right)+\left(96-95\right)+.....+\left(2-1\right)+\left(1-0\right)\)
\(=100+1+1+...+1+1\)
Vì lập được 49 cặp nên sẽ có 49 số 1
\(\Rightarrow E=100+1.49=100+49=149\)
đúng ko?
Đáp án A
Ta có : 3 5 4 = 3 × 4 + 5 4 = 12 + 5 4 = 17 4
Đáp án cần chọn là: A