Toán Lớp 8: Tìm x
a,x^3+x^2=4x+4
b,(2x-1)^2-(x-4)(1+4x)=1
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Toán Lớp 8: Tìm x
a,x^3+x^2=4x+4
b,(2x-1)^2-(x-4)(1+4x)=1
Comments ( 1 )
<=> x^3+x^2-4x-4=0
<=> x^2(x+1)-4(x+1)=0
<=> (x+1)(x^2-4)=0
<=> (x+1)(x-2)(x+2)=0
<=> [(x+1=0),(x-2=0),(x+2=0):}
<=> [(x=-1),(x=2),(x=-2):}
Vậy S={-2;-1;2}
b. (2x-1)^2-(x-4)(1+4x)=1
<=> 4x^2-4x+1-(x+4x^2-4-16x)=1
<=> 4x^2-4x+1-x-4x^2+4+16x=1
<=> 11x+5=1
<=> 11x=-4
<=> x=-4/11
Vậy S={-4/11}