`a, 3(5x-1) - x(x-2) + x^2 - 13x = 7`.
`<=> 15x - 3 - x^2 + 2x + x^2 - 13x = 7`.
`<=> 4x = 10`.
`<=> x = 5/2`.
Vậy `x = 5/2`.
`b, 4(x+2) - 7(2x-1) + 9(3x-4) = 30`.`
`<=> 4x + 8 - 14x + 7 + 27x - 36 = 30`.`
`<=> 17x - 21 = 30`.
`<=> 17x = 51`.
`<=> x = 3.`
Vậy `x = 3.`
`c, (12x-5)(4x-1) + (3x-7)(1-16x)=81`.
`<=> 48x^2 - 32x + 5 - 48x^2+ 115x - 7 = 81`.
`<=> 83x = 83`
`<=> x = 1.`
Vậy `x = 1`.
`d, 2(3x-1)(2x+5) - 6(2x-1)(x+2) = -6`.
`<=> (3x-1)(2x+5)-3(2x-1)(x+2)=-3`.
`<=> 6x^2 + 13x - 5 - 6x^2 - 9x + 6 = -3`.
`<=> 4x = -2`
`<=> x = -1/2`.
Vậy `x = -1/2`
1) \(3\left(5x-1\right)-x\left(x-2\right)+x^2-13x=7\)
\(\Rightarrow15x-3-x^2+2x+x^2-13x=7\)
\(\Rightarrow4x-3=7\)
\(\Rightarrow4x=7+3\)
\(\Rightarrow x=\dfrac{10}{4}\)
\(\Rightarrow x=\dfrac{5}{2}\)
2) \(4\left(x+2\right)-7\left(2x-1\right)+9\left(3x-4\right)=30\)
\(\Rightarrow4x+8-14x+7+27x-36=30\)
\(\Rightarrow17x-21=30\)
\(\Rightarrow17x=21+30\)
\(\Rightarrow17x=51\)
\(\Rightarrow x=\dfrac{51}{17}\)
\(\Rightarrow x=2\)
3) \(\left(12x-5\right)\left(4x-1\right)+\left(3x-7\right)\left(1-16x\right)=81\)
\(\Rightarrow48x^2-12x-20x+5+3x-48x^2-7+112x=81\)
\(\Rightarrow83x-2=81\)
\(\Rightarrow83x=81+2\)
\(\Rightarrow x=\dfrac{83}{83}\)
\(\Rightarrow x=1\)
\(1,15x-3-x^2+2x+x^2-13x=7\\ 15x+2x-13x-x^2+x^2=7+3\\ 4x=10\\ x=\dfrac{5}{2}\\ 2,4x+8-14x+7+27x-36=30\\ 4x-14x+27x=30-8-7+36\\ 17x=51\\ x=3\)
\(3,48x^2-20x-12x+5+3x-7-48x^2+112x=81\\ 48x^2-48x^2-20x-12x+3x+112x=81+7-5\\ 83x=83\\ x=1\)
\(4,2\left(6x^2-2x+15x-5\right)-6\left(2x^2-x+4x-2\right)=-6\\ 12x^2-4x+30x-10-12x^2+6x-24x+12=-6\\ 12x^2-12x^2-4x+30x+6x-24x=-6-12+10\\ 8x=-8\\ x=-1\)