Toán Lớp 7: `c,` `3x-|3x-5|=8` `d,` `|2x+6|=9x-4`

Question

Toán Lớp 7:  c, 3x-|3x-5|=8 d, |2x+6|=9x-4

hoaiphuong85 · Answer

Giải đáp+Lời giải và giải thích chi tiết:     c, 3x - |3x-5| =8   -> |3x-5| = 3x-8    ->  ( left[  begin{array}{l}3x-5=3x-8  3x-5=-3x+8 end{array}  right. )    ->  ( left[  begin{array}{l}3x-3x=-8+5  3x+3x=8+5 end{array}  right. )    ->  ( left[  begin{array}{l}0x = -3 (v&ocirc; l&yacute;)  6x=13&rarr; x=13/6 end{array}  right. )     d, |2x+6| = 9x-4    ->  ( left[  begin{array}{l}2x+6=9x-4  2x+6=-9x+4 end{array}  right. )    ->  ( left[  begin{array}{l}2x-9x=-4-6  2x+9x=4-6 end{array}  right. )    ->  ( left[  begin{array}{l}-7x = -10  11x=-2 end{array}  right. )    ->  ( left[  begin{array}{l}x=10/7  x=-2/11 end{array}  right. )

cobelolen · Answer

Giải đáp:   c)  3x - | 3x -5| =8   => | 3x -5| = 3x -8   $  Rightarrow left[ begin{matrix} 3x -5 = 3x -8   3x-5=- 3x + 8 end{matrix} right.$   $  Rightarrow left[ begin{matrix} 3x - 3x  = -8 + 5   3x + 3x = 8 + 5 end{matrix} right.$   $  Rightarrow left[ begin{matrix} 0x  = -3   6x = 13  end{matrix} right.$   $  Rightarrow left[ begin{matrix} 0x  = -3   x = 13/6  end{matrix} right.$   d)  | 2x + 6| = 9x -4   $  Rightarrow left[ begin{matrix} 2x + 6 = 9x -4   2x + 6 = -9x + 4  end{matrix} right.$   $  Rightarrow left[ begin{matrix} 2x - 9x = -4 -6   2x + 9x =  4 -6  end{matrix} right.$   $  Rightarrow left[ begin{matrix} -7x = -10   11x =  -2  end{matrix} right.$   $  Rightarrow left[ begin{matrix} x =10/7    x =  -2/11  end{matrix} right.$   S ={ 10/7 ; -2/11}