Đáp án:
`a)S={14/23}`
`b)S={8/5}`
`c)S={45/16}`
`d)S={43/25}`
Giải thích các bước giải:
`a)(3x-7)(4x-2)-5x(2x-1)=2x(x-3)`
`⇔12x²-6x-28x+14-10x²+5x=2x²-6x`
`⇔(12x²-10x²)+(-6x-28x+5x)+14=2x²-6x`
`⇔2x²-29x+14=2x²-6x`
`⇔2x²-29x-2x²+6x=-14`
`⇔-23x=-14`
`⇔x=14/23`
Vậy `S={14/23}`
`b)(4x-3)(9x-7)-(6x-5)²=4`
`⇔36x²-28x-27x+21-(36x²-60x+25)=4`
`⇔36x²-28x-27x+21-36x²+60x-25=4`
`⇔(36x²-36x²)+(-28x-27x+60x)+(21-25)=4`
`⇔5x-4=4`
`⇔5x=4+4`
`⇔5x=8`
`⇔x=8/5`
Vậy `S={8/5}`
`c)(2x-5)(2x+5)-(2x-3)²=7-4(x-1)`
`⇔4x²-25-(4x²-12x+9)=7-4x+4`
`⇔4x²-25-4x²+12x-9=-4x+11`
`⇔(4x²-4x²)+12x+(-25-9)=-4x+11`
`⇔12x-34=-4x+11`
`⇔12x+4x=11+34`
`⇔16x=45`
`⇔x=45/16`
Vậy `S={45/16}`
`d)(3x-7)²-(5+3x)(3x-5)=4(2x-3)`
`⇔9x²-42x+49-(9x²-25)=8x-12`
`⇔9x²-42x+49-9x²+25=8x-12`
`⇔(9x²-9x²)-42x+(49+25)=8x-12`
`⇔-42x+74=8x-12`
`⇔-42x-8x=-12-74`
`⇔-50x=-86`
`⇔x=86/50`
`⇔x=43/25`
Vậy `S={43/25}`
