a: \(\Leftrightarrow7\left(7-3x\right)+12\left(5x+2\right)=84\left(x+13\right)\)
\(\Leftrightarrow49-21x+60x+24=84x+1092\)
\(\Leftrightarrow39x-84x=1092-73\)
=>-45x=1019
hay x=-1019/45
b: \(\Leftrightarrow21\left(x+3\right)-14=4\left(5x+9\right)-7\left(7x-9\right)\)
=>21x+63-14=20x+36-49x+63
=>21x+49=-29x+99
=>50x=50
hay x=1
c: \(\Leftrightarrow7\left(2x+1\right)-3\left(5x+2\right)=21x+63\)
=>14x+7-15x-6-21x-63=0
=>-22x-64=0
hay x=-32/11
d: \(\Leftrightarrow35\left(2x-3\right)-15\left(2x+3\right)=21\left(4x+3\right)-17\cdot105\)
=>70x-105-30x-45=84x+63-1785
=>40x-150-84x+1722=0
=>-44x+1572=0
hay x=393/11
a, msc 12.7=84
Chuyển vế về =0 rồi làm
b,msc 28
c,làm tương tự
a, \(\Rightarrow49-21x+60x+24=84x+1092\)
\(\Leftrightarrow-45x=1019\Leftrightarrow x=-\dfrac{1019}{45}\)
b, \(\Rightarrow21\left(x+3\right)-14=4\left(5x+9\right)-7\left(7x-9\right)\)
\(\Leftrightarrow21x+63-14=20x+36-49x+63\)
\(\Leftrightarrow50x=50\Leftrightarrow x=1\)
c, \(\Rightarrow14x+7-15x-6=21x+63\Leftrightarrow-22x=62\Leftrightarrow x=-\dfrac{31}{11}\)
d, \(\Rightarrow35\left(2x-3\right)-15\left(2x+3\right)=21\left(4x+3\right)-105.17\)
\(\Leftrightarrow70x-105-30x-45=84x+63-1785\)
\(\Leftrightarrow-44x=-1572\Leftrightarrow x=\dfrac{393}{11}\)
a)
\(\dfrac{7-3x}{12}+\dfrac{5x+2}{7}=x+13\\ \Leftrightarrow\dfrac{7.\left(7-3x\right)}{84}+\dfrac{12\left(5x+2\right)}{84}=\dfrac{84.\left(x+13\right)}{84}\\ \Leftrightarrow49-21x+60x+24=84x+1092\\ \Leftrightarrow-21x+60x-84x=1092-49-24\\ \Leftrightarrow-45x=1019\\ \Leftrightarrow x=\dfrac{-1019}{45}\)
Vậy PT có tập nghiệm S = { \(\dfrac{-1019}{45}\) }
b) \(\dfrac{3\left(x+3\right)}{4}-\dfrac{1}{2}=\dfrac{5x+9}{7}-\dfrac{7x-9}{4}\\ \Leftrightarrow\dfrac{21\left(x+3\right)}{28}-\dfrac{14}{28}=\dfrac{4\left(5x+9\right)}{28}-\dfrac{7\left(7x-9\right)}{28}\\ \Leftrightarrow21x+63-14=20x+36-49x+63\\ \Leftrightarrow21x-20x+49x=36-63+14\\ \Leftrightarrow50x=-13\\ \Leftrightarrow x=\dfrac{-13}{50}\)
Vậy PT có tập nghiệm S = { \(\dfrac{-13}{50}\) }