A=2/3+|5-x|
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a) \(2+2+2+2+2=2\times5=10\)
\(2\times5=10\)
\(5+5=2\times5=10\)
\(5\times2=10\)
b) \(3\times5=3+3+3+3+3=15\)
\(5\times3=5+5+5=15\)
\(3\times5=5+5+5=15\)
\(5\times3=3+3+3+3+3=15\)
a) 2 + 2 + 2 + 2 + 2 = 10
2 x 5 = 10
5 + 5 = 10
5 x 2 = 10
b) 3 x 5 = 3 + 3 + 3 + 3 + 3 = 15
5 x 3 = 5 + 5 + 5 = 15
3 x 5 = 15
5 x 3 = 15
Bài 1
a) 3 2/5 - 1/2
= 17/5 - 1/2
= 34/10 - 5/10
= 29/10
b) 4/5 + 1/5 × 3/4
= 4/5 + 3/20
= 16/20 + 3/20
= 19/20
c) 3 1/2 × 1 1/7
= 7/2 × 8/7
= 4
d) 4 1/6 : 2 1/3
= 25/6 : 7/3
= 25/14
Bài 2
a) 3 × 1/2 + 1/4 × 1/3
= 3/2 + 1/12
= 18/12 + 1/12
= 19/12
b) 1 4/5 - 2/3 : 2 1/3
= 9/5 - 2/3 : 7/3
= 9/5 - 2/7
= 63/35 - 10/35
= 53/35
a: =>x-2/5=3/4:1/3=3/4*3=9/4
=>x=9/4+2/5=45/20+8/20=53/20
b: =>x-2/3=7/3:4/5=7/3*5/4=35/12
=>x=35/12+2/3=43/12
c: 1/3(x-2/5)=4/5
=>x-2/5=4/5*3=12/5
=>x=12/5+2/5=14/5
d: =>2/3x-1/3-1/4x+1/10=7/3
=>5/12x-7/30=7/3
=>5/12x=7/3+7/30=77/30
=>x=77/30:5/12=154/25
e: \(\Leftrightarrow x\cdot\dfrac{3}{7}-\dfrac{2}{7}+\dfrac{1}{2}-\dfrac{5}{4}x+\dfrac{5}{2}=0\)
=>\(x\cdot\dfrac{-23}{28}=\dfrac{2}{7}-3=\dfrac{-19}{7}\)
=>x=19/7:23/28=76/23
f: =>1/2x-3/2+1/3x-4/3+1/4x-5/4=1/5
=>13/12x=1/5+3/2+4/3+5/4=257/60
=>x=257/65
i: =>x^2-2/5x-x^2-2x+11/4=4/3
=>-12/5x=4/3-11/4=-17/12
=>x=17/12:12/5=85/144
\(\begin{array}{l}a)A = 3x - 4{x^4} + {x^3}\\ = - 4{x^4} + {x^3} + 3x\\b)B = - 2{x^3} - 5{x^2} + 2{x^3} + 4x + {x^2} - 5\\ = ( - 2{x^3} + 2{x^3}) + \left( { - 5{x^2} + {x^2}} \right) + 4x - 5\\ = 0 + ( - 4{x^2}) + 4x - 5\\ = - 4{x^2} + 4x - 5\\c)C = {x^5} - \dfrac{1}{2}{x^3} + \dfrac{3}{4}x - {x^5} + 6{x^2} - 2\\ = \left( {{x^5} - {x^5}} \right) - \dfrac{1}{2}{x^3} + 6{x^2} + \dfrac{3}{4}x - 2\\ = - \dfrac{1}{2}{x^3} + 6{x^2} + \dfrac{3}{4}x - 2\end{array}\)
`@` `\text {Ans}`
`\downarrow`
`a,`
`2/5 + x = 2/7`
`=> x = 2/7 -2/5`
`=> x= - 4/35`
Vậy, `x=-4/35`
`b,`
`x + 3/5 = -2/5`
`=> x = -2/5 - 3/5`
`=> x=-1`
Vậy, `x=-1`
`c, `
`x - 8/5 = 3/7`
`=> x=3/7 + 8/5`
`=> x=71/35`
Vậy, `x=71/35`
`d,`
`3/5 - x = 7/3`
`=> x=3/5 - 7/3`
`=> x=-26/15`
Vậy, `x=-26/15`
a) \(\dfrac{2}{5}+x=\dfrac{2}{7}\)
\(\Rightarrow x=\dfrac{2}{7}-\dfrac{2}{5}\)
\(\Rightarrow x=-\dfrac{4}{35}\)
b) \(x+\dfrac{3}{5}=-\dfrac{2}{5}\)
\(\Rightarrow x=-\dfrac{2}{5}-\dfrac{3}{5}\)
\(\Rightarrow x=-1\)
c) \(x-\dfrac{8}{5}=\dfrac{3}{7}\)
\(\Rightarrow x=\dfrac{3}{7}+\dfrac{8}{5}\)
\(\Rightarrow x=\dfrac{71}{35}\)
d) \(\dfrac{3}{5}-x=\dfrac{7}{3}\)
\(\Rightarrow x=\dfrac{3}{5}-\dfrac{7}{3}\)
\(\Rightarrow x=-\dfrac{26}{15}\)
Bài 1:
a) \(-5\left(x^2-3x+1\right)+x\left(1+5x\right)=x-2\)
\(\Rightarrow-5x^2+15x-5+x+5x^2=x-2\)
\(\Rightarrow16x-5=x-2\)
\(\Rightarrow16x-x=5-2\)
\(\Rightarrow15x=3\)
\(\Rightarrow x=\dfrac{15}{3}=5\)
b) \(12x^2-4x\left(3x+5\right)=10x-17\)
\(\Rightarrow12x^2-12x^2-20x=10x-17\)
\(\Rightarrow-20x=10x-17\)
\(\Rightarrow-20x-10x=-17\)
\(\Rightarrow-30x=-17\)
\(\Rightarrow x=\dfrac{-30}{-17}=\dfrac{30}{17}\)
c) \(-4x\left(x-5\right)+7x\left(x-4\right)-3x^2=12\)
\(\Rightarrow-4x^2+20x+7x^2-28x-3x^2=12\)
\(\Rightarrow-8x=12\)
\(\Rightarrow x=\dfrac{12}{-8}=-\dfrac{4}{3}\)
Bài 2:
a) \(\left(x+5\right)\left(x-7\right)-7x\left(x-3\right)\)
\(=x^2-7x+5x-35-7x^2+21x\)
\(=-6x^2+19x-35\)
b) \(x\left(x^2-x-2\right)-\left(x-5\right)\left(x+1\right)\)
\(=x^3-x^2-2x-x^2+x-5x-5\)
\(=x^3-2x^2-6x-5\)
c) \(\left(x-5\right)\left(x-7\right)-\left(x+4\right)\left(x-3\right)\)
\(=x^2-7x-5x+35-x^2-3x+4x-12\)
\(=11x+23\)
d) \(\left(x-1\right)\left(x-2\right)-\left(x+5\right)\left(x+2\right)\)
\(=x^2-2x-x+2-x^2+2x+5x+10\)
\(=4x+12\)