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a) 320 x 63 - 16 x 20 + 32 x 370
= 320 x 63 - 320 x + 320 x 37
= 320 x ( 63 - 1 + 37 )
= 320 x 99
= 320 x ( 100 - 1 )
= 320 x 100 - 320
= 32000 - 320 = 31 680
b) 35 x 61 + 215 x 5 + 35 x 39 + 57 x 25
= 5 x 427 + 5 x 215 + 5 x 273 + 5 x 285
= 5 x ( 427 + 215 + 273 + 285 )
= 5 x 1200 = 6000
c) 34 x 24 - 94 x 6 + 83 x 48 - 47 x 88
= 204 x 4 - 4 x 141 + 996 x 4 - 1034 x 4
= 4 x ( 204 - 141 + 996 - 1034 )
= 4 x 25 = 100
a)\(x-\left(-24\right)=3\)
\(x+24=3\)
\(x=3-24\)
\(x=-21\)
b)\(22-\left(-x\right)=12\)
\(\Rightarrow22+x=12\)
\(\Rightarrow x=12-22\)
\(\Rightarrow x=-10\)
c) \(\left(27-x\right)+\left(15+x\right)=x-24\)
\(\Rightarrow27-x+15+x=x-24\)
\(\Rightarrow42=x-24\)
\(\Rightarrow66=x\)
d)\(x+x-\left(-4\right)=x+2\)
\(\Rightarrow x+x+4=x+2\)
\(\Rightarrow x+x-x=2-4\)
\(\Rightarrow x=-2\)
câu 2 :
\(-37+54+\left(-70\right)+9-163+246\)
\(=\left(-37-163\right)+\left(246+54\right)+\left(-70\right)+9\)
\(=-200+200+-61\)
\(=-61\)
1a) -54 . 76 + 12 .(-76) + 76.(-34)
= (-54 - 12 - 34).76
= -100 . 76
= -176
b) 37.(63 - 24) - 63.(24 + 37)
= 37 . 63 - 37 . 24 - 63.24 - 63 . 37
= (37.63 - 63.37) - (37 + 63) . 24
= 0 - 100 . 24
= - 2400
2a) x + (-27) = -23 - x
=> x + x = -23 + 27
=> 2x = 4
=> x = 4 : 2
=> x = 2
b) xy + 2x - y = 15
=> x(y + 2) - y = 15
=> x(y + 2) - (y + 2) = 13
=> (x - 1)(y + 2) = 13 = 1 . 13 = 13 . 1
Lập bảng :
x - 1 | 1 | -1 | 13 | -13 |
y + 2 | 13 | -13 | 1 | -1 |
x | 2 | 0 | 14 | -12 |
y | 11 | -15 | -1 | -3 |
Vậy ...
Sửa đề
\(\dfrac{3}{35}+\dfrac{3}{63}+\dfrac{3}{99}+...+\dfrac{3}{x\left(x+2\right)}=\dfrac{24}{35}\)
\(\dfrac{3}{5.7}+\dfrac{3}{7.9}+\dfrac{3}{9.11}+...+\dfrac{3}{x\left(x+2\right)}=\dfrac{24}{35}\)
\(\dfrac{3}{2}.\left(\dfrac{2}{5.7}+\dfrac{2}{7.9}+...+\dfrac{2}{x\left(x+2\right)}\right)=\dfrac{24}{35}\)
\(\dfrac{3}{2}.\left(\dfrac{1}{5}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{9}+...+\dfrac{1}{x}-\dfrac{1}{x+2}\right)=\dfrac{24}{35}\)
\(\dfrac{3}{2}.\left(\dfrac{1}{5}-\dfrac{1}{x+2}\right)=\dfrac{24}{35}\)
\(\dfrac{1}{5}-\dfrac{1}{x+2}=\dfrac{24}{35}:\dfrac{3}{2}\)
\(\dfrac{1}{5}-\dfrac{1}{x+2}=\dfrac{16}{35}\)
\(\dfrac{1}{x+2}=\dfrac{1}{5}-\dfrac{16}{35}\)
\(\dfrac{1}{x+2}=\dfrac{-9}{35}\)
\(x+2=35\)
\(x=35-2\)
\(x=33\)
\(-17x=-17-\left(-34\right)\)
\(-17x=-17\)
\(x=-1\)
Bạn coi lại đề: $\frac{3}{69}$ không nằm trong các số hạng có quy luật.
tìm số tự nhiên x lớn nhất biết
a, 24 : x , 36 : x
b , 32 : x , 48 : x
c , 24 : x , 84 : x , 180 : x
a) 24 = 23 . 3
36 = 22 . 33
ƯCLN(24,36) = 22 . 3 = 4 . 3 = 12
b) 32 = 25
48 = 24 . 3
ƯCLN(32,48) = 24 = 16
c) 24 = 23 . 3
84 = 22 . 3 . 7
180 = 22 . 32 . 5
ƯCLN(24,84,180) = 22 . 3 = 4 . 3 = 12
a)\(\dfrac{x}{60}=-\dfrac{3}{4}\)
\(\Rightarrow x\cdot4=60\cdot\left(-3\right)\)
\(x\cdot4=-180\)
x=45
b)\(\dfrac{2}{5}=\dfrac{12}{x}\)
\(\Rightarrow2x=5\cdot12\)
\(2x=60\)
x=30
c)\(x-\dfrac{5}{7}=\dfrac{6}{21}\)
\(x=\dfrac{2}{7}+\dfrac{5}{7}\)
x=1
d)\(x+\dfrac{7}{8}=\dfrac{63}{24}\)
\(x=\dfrac{21}{8}-\dfrac{7}{8}\)
\(\dfrac{14}{8}\)
\(24\times163-24\times63+32\\ =24\times\left(163-63\right)+32\\ =24\times100+32\\ =2400+32=2432\)
\(24\cdot163-24\cdot63+32\)
\(=24\cdot\left(163-63\right)+32\)
\(=24\cdot100+32\)
\(=2400+32\)
\(=2432\)