Đáp án:
`(3x + 5)^2 - 9x(x - 2) + (2x - 3)^3 = (2x + 1)(4x^2 - 2x + 1) - 18x(2x - 3)`
`⇔ (3x)^2 + 2.3x.5 + 5^2 - 9x^2 + 18x + (2x)^3 - 3.(2x)^2.3 + 3.2x.3^2 - 3^3 = (2x + 1)[(2x)^2 - 2x.1 + 1^2] - 36x^2 + 54x`
`⇔ 9x^2 + 30x + 25 - 9x^2 + 18x + 8x^3 - 36x^2 + 54x - 27 = (2x)^3 + 1^3 - 36x^2 + 54x`
`⇔ 9x^2 + 30x + 25 - 9x^2 + 18x + 8x^3 - 36x^2 + 54x - 27 = 8x^3 +1 - 36x^2 + 54x`
`⇔ 9x^2 + 30x + 25 - 9x^2 + 18x + 8x^3 - 36x^2 + 54x - 27 - 8x^3 - 1 + 36x^2 - 54x = 0`
`⇔ (9x^2 - 9x^2 - 36x^2 + 36x^2) + (8x^3 - 8x^3) + (30x + 18x + 54x - 54x) + (25 - 27 - 1) = 0`
`⇔ 48x - 3 = 0`
`⇒ 48x = 3`
`⇒ x = 3/48`
`⇒ x = 1/16`
Học tốt
