Câu 1
`a)(2x-3)(x+1)-2x(-5)=14`
`<=> 2x^2+2x-3x-3+10x=14`
`<=> 2x^2+9x-17=0`
Tính `Δ=9^2 - 4 · 2 · (-17) = 217 > 0`
`=>` `pt` có `2` nghiệm pb
`x_1 =` $\dfrac{-9+\sqrt{217}}{4}$
`x_2 =` $\dfrac{-9-\sqrt{217}}{4}$
`b)(4x^9)-8(2x+3)=0`
`<=> 4x^9 -16x-24=0`
`<=> 4(x^9 -4x-6)=0`
`<=> x^9 - 4x - 6 =0`
`c)(2x-3)(x+1)-2x(x-15)`
`<=> 2x^2+2x-3x-3-2x^2+30x=0`
`<=> 29x = -3`
`<=> x = -3/29`