Toán Lớp 8: Tìm x:
a, 2x^2 – 4x = 0
b, (3x-2)^2 – 9x^2 = 0
c, x^2 – 3x = 0
d, (2x+1)^2 – 4x^2 = 0
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Toán Lớp 8: Tìm x:
a, 2x^2 – 4x = 0
b, (3x-2)^2 – 9x^2 = 0
c, x^2 – 3x = 0
d, (2x+1)^2 – 4x^2 = 0
Comments ( 2 )
a)
2x^2-4x=0
<=>2x.x-2x.2=0
<=>2x(x-2)=0
<=>[(x=0),(x-2=0):}
<=>[(x=0),(x=2):}
Vậy x\in{0;2}
b)
(3x-2)^2-9x^2=0
<=>(3x-2)^2-(3x)^2=0
<=>(3x-2-3x)(3x-2+3x)=0
<=>-2.(6x-2)=0
<=>6x-2=0
<=>6x=2
<=>x=1/3
Vậy x=1/3
c)
x^2-3x=0
<=>x.(x-3)=0
<=>[(x=0),(x-3=0):}
<=>[(x=0),(x=3):}
Vậy x\in{0;3}
d)
(2x+1)^2-4x^2=0
<=>(2x+1)^2-(2x)^2=0
<=>(2x+1-2x)(2x+1+2x)=0
<=>1.(4x+1)=0
<=>4x+1=0
<=>4x=-1
<=>x=-1/4
Vậy x=-1/4