Toán Lớp 9: a) (2x^2 + 3x)^2 = 2x + 6x^3 – 4
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Toán Lớp 9: a) (2x^2 + 3x)^2 = 2x + 6x^3 – 4
Comments ( 1 )
$\left(2x^2\:+\:3x\right)^2\:=\:2x\:+\:6x^3\:-\:4$
$⇒4x^4+12x^3+9x^2=2x+6x^3-4$
$⇒4x^4+12x^3+9x^2+4=2x+6x^3-4+4$
$⇒4x^4+12x^3+9x^2+4=2x+6x^3$
$⇒4x^4+12x^3+9x^2+4-6x^3=2x+6x^3-6x^3$
$⇒4x^4+6x^3+9x^2+4=2x$
$⇒4x^4+6x^3+9x^2+4-2x=2x-2x$
$⇒4x^4+6x^3+9x^2-2x+4=0$
Vậy không có giá trị x nào.