Gửi bn

a) $\dfrac{3(3x+2}{6}$-$\dfrac{3x+1}{6}$=$\dfrac{2.50}{6}$+$\dfrac{6.2x}{6}$

⇒$\dfrac{9x+6}{6}$-$\dfrac{3x+1}{6}$=$\dfrac{100}{6}$+$\dfrac{12x}{6}$

⇔9x+6-3x+1=100+12x

⇔9x-3x-12x=-6-1+100

⇔-6x=93

⇔x=$\dfrac{-31}{2}$

S={$\dfrac{-31}{2}$}

b) $\dfrac{21(4x+3}{105}$ - $\dfrac{15(6x-2)}{105}$=$\dfrac{35(5x+4}{105}$+$\dfrac{105.3}{105}$

⇔$\dfrac{84x+63}{105}$ - $\dfrac{90x-30}{105}$=$\dfrac{175x+140}{105}$+$\dfrac{315}{105}$

⇒84x+63-90x-30=175x+140+315

⇔84x-90x-175x=-63+30+140+315

⇔-181x=422

⇔x=$\dfrac{-422}{181}$

S={$\dfrac{-422}{181}$}

c)$\dfrac{6(x+4)}{30}$-$\dfrac{30(x+4)}{30}$=$\dfrac{10.x}{30}$-$\dfrac{15(x-2)}{30}$

⇔$\dfrac{6x+24}{30}$-$\dfrac{30x+120}{30}$=$\dfrac{10x}{30}$-$\dfrac{15x-30}{30}$

⇒6x+24-30x+120=10x-15x-30

⇔6x-30x-10x+15x=-24-120+30

⇔-19x=-114

⇔x=6

S={6}

d)$\dfrac{15(5x+2)}{90}$-$\dfrac{30(8x-1)}{90}$=$\dfrac{18(4x+2)}{90}$-$\dfrac{90.5}{90}$

⇔$\dfrac{75x+30}{90}$-$\dfrac{240x-30}{90}$=$\dfrac{72x+36}{90}$-$\dfrac{450}{90}$

⇒75x+30-240x-30=72x+36-450

⇔75x-240x-72x=-30+30+36-450

⇔-237x=-414

⇔x=$\dfrac{138}{79}$

S={$\dfrac{138}{79}$}