Toán Lớp 8: tìm x biết
a) 6x(x-2)+3x=6x²+10
b) (2x+1)(x-4)=(2x+1)²
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Toán Lớp 8: tìm x biết
a) 6x(x-2)+3x=6x²+10
b) (2x+1)(x-4)=(2x+1)²
Comments ( 2 )
6x(x-2)+3x=6x^2+10
<=>6x^2-12x+3x=6x^2+10
<=>6x^2-9x=6x^2+10
<=>6x^2-9x-6x^2-10=0
<=>-9x-10=0
<=>-9x=10
<=>x=-10/9
Vậy x=-10/9
b)
(2x+1)(x-4)=(2x+1)^2
<=>(2x+1)(x-4)-(2x+1)^2=0
<=>(2x+1)(x-4)-(2x+1)(2x+1)=0
<=>(2x+1)(x-4-2x-1)=0
<=>(2x+1)(-x-5)=0
<=>[(2x+1=0),(-x-5=0):}
<=>[(2x=-1),(-x=5):}
<=>[(x=-1/2),(x=-5):}
Vậy x=-1/2;x=-5