Toán Lớp 8: Tìm x,biết: (2x+3).(x-4)+(x-5).(x-2)=(3x-5).(x-4)
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Toán Lớp 8: Tìm x,biết: (2x+3).(x-4)+(x-5).(x-2)=(3x-5).(x-4)
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<=>2x(x-4)+3(x-4)+x(x-2)-5(x-2)=3x(x-4)-5(x-4)
<=>2x^2-8x+3x-12+x^2-2x-5x+10=3x^2-12x-5x+20
<=>(2x^2+x^2)+(-8x+3x-2x-5x)+(-12+10)=3x^2-(12x+5x)+20
<=>3x^2-12x-2=3x^2-17x+20
<=>3x^2-12x-2-3x^2+17x-20=0
<=>(3x^2-3x^2)+(17x-12x)+(-2-20)=0
<=>5x-22=0
<=>5x=22
<=>x=22/5
Vậy phương trình có nghiệm S={22/5}