∛(12-x) + ∛(4+x)=2
Tính nhẩm:
3 x 4 = 12 2 x 5 = 5 x 3 = 4 x 2 =
12 : 3 = 10 : 2 = 15 : 3 = 8 : 2 =
12 : 4 = 10 : 5 = 15 : 5 = 8 : 4 =
Ta tính nhẩm như sau:
3x4=12 2x5=10 5x3=15 4x2=8
12:3=4 10:2=5 15:3=5 8:2=4
12:4=3 10:5=2 15:5=3 8:4=2
3x4 = 12 2x5 = 10 5x3 = 15 4x2 =8
12 : 3 = 4 10 : 2 = 5 15 : 3 = 5 8 : 2 = 4
12 : 4 =3 10 :5 = 2 15 : 5 = 3 8 : 4 = 2
1/ \(\dfrac{x+4}{4}+\dfrac{3x-7}{5}=\dfrac{7x+2}{20}\)
2/ \(\dfrac{x}{6}+\dfrac{1-3x}{9}=\dfrac{-x+1}{12}\)
3/ \(\dfrac{x-3}{3}-\dfrac{x+2}{12}=\dfrac{2x-1}{4}\)
4/ \(\dfrac{x-2}{4}-\dfrac{2x+3}{3}=\dfrac{x+6}{12}\)
5/ \(\dfrac{2x-1}{12}-\dfrac{3-x}{18}=\dfrac{-1}{36}\)
1: Ta có: \(\dfrac{x+4}{4}+\dfrac{3x-7}{5}=\dfrac{7x+2}{20}\)
\(\Leftrightarrow5x+20+12x-28=7x+2\)
\(\Leftrightarrow17x-7x=2+8=10\)
hay x=1
2: Ta có: \(\dfrac{x}{6}+\dfrac{1-3x}{9}=\dfrac{-x+1}{12}\)
\(\Leftrightarrow\dfrac{6x}{36}+\dfrac{4\left(1-3x\right)}{36}=\dfrac{3\left(-x+1\right)}{36}\)
\(\Leftrightarrow6x+4-12x=-3x+3\)
\(\Leftrightarrow-6x+3x=3-4\)
hay \(x=\dfrac{1}{3}\)
3: Ta có: \(\dfrac{x-3}{3}-\dfrac{x+2}{12}=\dfrac{2x-1}{4}\)
\(\Leftrightarrow4x-12-x-2=6x-3\)
\(\Leftrightarrow3x-14-6x+3=0\)
\(\Leftrightarrow-3x=11\)
hay \(x=-\dfrac{11}{3}\)
4: Ta có: \(\dfrac{x-2}{4}-\dfrac{2x+3}{3}=\dfrac{x+6}{12}\)
\(\Leftrightarrow3x-6-8x-12=x+6\)
\(\Leftrightarrow-5x-x=6+18\)
hay x=-4
5: Ta có: \(\dfrac{2x-1}{12}-\dfrac{3-x}{18}=\dfrac{-1}{36}\)
\(\Leftrightarrow6x-3+2x-6=-1\)
\(\Leftrightarrow8x=8\)
hay x=1
Tính nhanh
Ạ) ( 12 x 2 + 12 x 4 - 12 x 6) : ( 2 + 4 + 6 +... + 12 + 14)
b) 37 x 49 + 37 x 2 x 25 + 37
A) (12 x 2 + 12 x 4 + 12 x 6) : ( 2 + 4 + 6 + ... + 12 + 14)
= [12 x ( 2 + 4 - 6 )] : ( 2 + 4 + 6 + ... + 12 + 14)
= [12 x 0 ] : ( 2 + 4 + 6 + ... + 12 + 14)
= 0 : ( 2 + 4 + 6 + ... + 12 + 14)
= 0
B) 37 x 49 + 37 x 2 x 25 + 37
= 37 x (49 + 2 x 25 + 1)
= 37 x 100
= 3700
Học dỏi nha :)))
~ Good luck ~
Sai cái dì mà mí người k sai nhiều quá v ?? :D ??
Tính nhanh:
A = ( 12 x 2 + 12 x 4 +12 x 6 ) : ( 2 + 4 + .......... + 12 + 14 )
Ta gọi vế \(\left(12\cdot2+12\cdot4+12\cdot6\right)\)là vế \(\left(1\right)\)
Ta gọi vế \(\left(2+4+...+12+14\right)\)là vế \(\left(2\right)\)
\(\left(1\right):\)\(12\cdot\left(2+4+6\right)=12\cdot12=144\)
\(\left(2\right):\)\(\frac{\left(14-2\right)}{2}+1=7\)( số )\(=\left(14+2\right)\cdot\frac{7}{2}=28\)
Vậy ta có \(:\)
\(A=\frac{144}{56}=2.5714\)
Đáp số : \(2.5714\)
tinh nhanh
a=(12 x 4 + 12 x 2 -12 x 6) : (2 + 4 + ... + 12 + 14 )
12 x 4 + 12 x 2 -12 x 6=0
0 chưa cho số nào cũng bằng không
0 nha
12 x 2 x 4 x 6 + 6 : 4 : 2 : 12
\(12\times2\times4\times6+6:4:2:12=576,0625\)
Tính bằng hai cách (theo mẫu).
Mẫu: 4 x 3 x 2 = ..?.. Cách 1: 4 x 3 x 2 = (4 x 3) x 2 = 12 = 12 x 2 = 24 Cách 2: 4 x 3 x 2 = 4 = 4 x (3 x 2) = 4 x 6 = 24 |
4 x 2 x 5 7 x 2 x 3 6 x 3 x 3 6 x 2 x 4
4 x 2 x 5 = ?
Cách 1: 4 x 2 x 5 = (4 x 2) x 5 = 8 x 5 = 40
Cách 2: 4 x 2 x 5 = 4 x (2 x 5) = 4 x 10 = 40
7 x 2 x 3 = ?
Cách 1: 7 x 2 x 3 = (7 x 2) x 3 = 14 x 3 = 42
Cách 2: 7 x 2 x 3 = 7 x (2 x 3) = 7 x 6 = 42
6 x 3 x 3 = ?
Cách 1: 6 x 3 x 3 = (6 x 3) x 3 = 18 x 3 = 54
Cách 2: 6 x 3 x 3 = 6 x (3 x 3) = 6 x 9 = 54
6 x 2 x 4 = ?
Cách 1: 6 x 2 x 4 = (6 x 2) x 4 = 12 x 4 = 48
Cách 2: 6 x 2 x 4 = 6 x (2 x 4) = 6 x 8 = 48
Phân tích thành nhan tử
a) x^4 +x^3+6.x^2+5.x+5
b) x^4-2.x^3-12-12.x^2+12.x+36
c) x^8.y^8+x^4.y^4+1
Ta có : x4 + x3 + 6x2 + 5x + 5
= (x4 + 5x2) + (x3 + 5x) + (x2 + 5)
= x2(x2 + 5) + x(x2 + 5) + (x2 + 5)
= (x2 + 5)(x2 + x + 1)
a,3/4 . (-5/12)+3/4.(-7/12)
2. tìm x
a, 2/3 .x-0,5=3/4
b,3/x-2=-2/x-4 (đk x khác 2;x khác 4)
Bài 2:
a: =>2/3x=3/4+1/2=3/4+2/4=5/4
=>x=5/4:2/3=5/4*3/2=15/8
b:=>-2x+4=3x-12
=>-5x=-16
=>x=16/5
a,3/4 . (-5/12)+3/4.(-7/12)
2. tìm x
a, 2/3 .x-0,5=3/4
b,3/x-2=-2/x-4 (đk x khác 2;x khác 4)
a,3/4 . (-5/12)+3/4.(-7/12)
` 3/4 . [ - ( 5/12 + 7/12 ) ] `
`3/4 . (-1) = -3/4 `
`2/3 . x - 0,5 = 3/4 `
` x - 0,5 = 3/4 - 2/3 `
` x-0,5 = 1/12 `
` x = 1/12 + 0,5 `
` x= 7/12 `
a, 3/4 . (-5/12)+3/4.(-7/12)
= 3/4 . [(-5/12) + (-7/12)]
= 3/4 . (-1)
= -3/4
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a, 2/3 .x-0,5=3/4
2/3 . x = 3/2 + 0,5
2/3 . x = 2
x = 2 : 2/3
x = 3
vậy x = 3