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Bài 4:
a: =>3x=24
hay x=8
b: =>5x-2x=-11+3
=>3x=-8
hay x=-8/3
c: =>4/3x=17
hay x=51/4
d: =>3/7x=-8
hay x=-56/3
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a) 2x2y(x2+xy-3y2)
= 2x4y + 2x3y2 - 6x2y3
b) (2x+1)(x-1)
= 2x2 - 2x + x -1
= 2x2 -x -1
c) (3xy2+6x2y-9xy):3xy
= y + 2x - 3
d) \(\dfrac{2x+7}{x+1}+\dfrac{x-4}{x+1}\)
= \(\dfrac{2x+7+x-4}{x+1}\)
= \(\dfrac{3x+3}{x+1}\)
= \(\dfrac{3\left(x+1\right)}{x+1}\)= 3
e) \(\dfrac{\left(x+2\right)^2}{x-1}:\dfrac{x+2}{3x-3}\)
= \(\dfrac{\left(x+2\right)^2}{x-1}.\dfrac{3\left(x-1\right)}{x+2}\)
= 3(x+2) = 3x+6
f) \(\left(\dfrac{x^2+2x+2}{x+2}-\dfrac{1}{x+2}\right):\dfrac{x-1}{x+2}\)
= \(\left(\dfrac{x^2+2x+2-1}{x+2}\right):\dfrac{x-1}{x+2}\)
= \(\dfrac{x^2+2x+1}{x+2}.\dfrac{x+2}{x-1}\)
= \(\dfrac{\left(x+1\right)^2}{x-1}\)
Bổ sung: điều kiện n nguyên
Cách 1:
(2n+5)^2-25=4n^2+20n=4n(n+5) chia hết cho 4
Cách 2:
(2n+5)^2-25=2n(2n+10)=4n(n+5) chia hết cho 4