Tìm x biết: 5x(x – 3 )^2 – 5(x – 1 )^3 + 15(x + 2 )(x – 2 ) = 5 24/09/2021 Bởi Autumn Tìm x biết: 5x(x – 3 )^2 – 5(x – 1 )^3 + 15(x + 2 )(x – 2 ) = 5
TL: $5x(x−3)^2−5(x−1)^3+15(x+2)(x−2)=5$ $⇔ 5x(x^2−6x+9)−5(x^3−3x^2+3x−1)+15(x^2−4)=5$ $⇔ 5x^3−30x^2+45x−5x^3+15x^2−15x+5+15x^2−60=5$ $⇔ 30x=60$ $⇔x = 60 : 30$ $x = 2$ Bình luận
5x(x−3)^2−5(x−1)^3+15(x+2)(x−2)=5 ⇔ 5x(x^2−6x+9)−5(x^3−3x^2+3x−1)+15(x^2−4)=5 ⇔ 5x^3−30x^2+45x−5x^3+15x^2−15x+5+15x^2−60=5 ⇔ 30x=60 ⇔x=2 Bình luận
TL:
$5x(x−3)^2−5(x−1)^3+15(x+2)(x−2)=5$
$⇔ 5x(x^2−6x+9)−5(x^3−3x^2+3x−1)+15(x^2−4)=5$
$⇔ 5x^3−30x^2+45x−5x^3+15x^2−15x+5+15x^2−60=5$
$⇔ 30x=60$
$⇔x = 60 : 30$
$x = 2$
5x(x−3)^2−5(x−1)^3+15(x+2)(x−2)=5
⇔ 5x(x^2−6x+9)−5(x^3−3x^2+3x−1)+15(x^2−4)=5
⇔ 5x^3−30x^2+45x−5x^3+15x^2−15x+5+15x^2−60=5
⇔ 30x=60
⇔x=2