Toán Lớp 8: Tìm x, biết: 2x ( x – 1 ) + 10 = 2 ( x ² – 3 )
Rút gọn P = (2-x/x ²+x – 1/x+1) . x+1/x-1
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Toán Lớp 8: Tìm x, biết: 2x ( x – 1 ) + 10 = 2 ( x ² – 3 )
Rút gọn P = (2-x/x ²+x – 1/x+1) . x+1/x-1
Comments ( 2 )
Lời giải và giải thích chi tiết:
2x(x-1)+10=2(x^2 -3)
<=>2x^2 -2x+10=2x^2 -6
<=>-2x+10=-6
<=>-2x=-16
<=> x=8
Vậy x in {8}
P=((2-x)/(x^2 +x)-1/(x+1)) . (x+1)/(x-1) (x\ne0, x \ne+-1)
=((2-x)/(x(x+1))-x/(x(x+1))) . (x+1)/(x-1)
=(2-x-x)/(x(x+1)) . (x+1)/(x-1)
=(-2x+2)/(x(x+1)) . (x+1)/(x-1)
=(-2(x-1))/x . 1/(x-1)
=-2/x
2x ( x – 1 ) + 10 = 2 ( x ² – 3 )
<=>2x^2-2x+10=2x^2-6
<=>-2x=-6-10
<=>-2x=-16
<=>x=8
Vậy x=8
P = ((2-x)/(x ²+x) – 1/(x+1)) .( x+1)/(x-1)
=[(2-x)/(x(x +1)) – 1/(x+1)] .( x+1)/(x-1)
=((2-x)-x)/(x(x+1)).(x+1)/(x-1)
=(2-x-x)/(x(x+1)).(x+1)/(x-1)
=(2-2x)/(x(x+1)).(x+1)/(x-1)
=(-2(x-1))/(x(x+1)).(x+1)/(x-1)
=-2/x