Toán Lớp 7: /x+1/=/x-2/ b, 2 ×/x-2/+/2-x/=15

Question

Toán Lớp 7:  /x+1/=/x-2/ b, 2 ×/x-2/+/2-x/=15

maitrucloan · Answer

Giải đáp:   $  $   a,   |x+1| = |x-2|   ->  ( left[  begin{array}{l}x+1=x-2  x+1=-x+2 end{array}  right. )    ->  ( left[  begin{array}{l}x-x=1-2  x+x=-1+2 end{array}  right. )    ->  ( left[  begin{array}{l}0=-1  text{(V&ocirc; l&iacute;)}  x= dfrac{1}{2} end{array}  right. )    Vậy x=1/2   $  $   b,   2 |x-2| + |2-x|=15   -> 2 |x-2| + |x-2|=15   -> |x-2| (2+1)=15   -> 3 |x-2|=15   -> |x-2|=15&divide;3   -> |x-2|=5   ->  ( left[  begin{array}{l}x-2=5  x-2=-5 end{array}  right. )    ->  ( left[  begin{array}{l}x=5+2  x=-5+2 end{array}  right. )    ->  ( left[  begin{array}{l}x=7  x=-3 end{array}  right. )    Vậy x=7 hoặc x=-3

cobexinhdep · Answer

|x+1|=|x-2|   $ leftrightarrow  left[  begin{array}{l}x+1=x-2  x+1=-(x-2) end{array}  right.$   $ leftrightarrow  left[  begin{array}{l}x in&empty;  x= dfrac{1}{2} end{array}  right.$   $ leftrightarrow x= dfrac{1}{2}$   Vậy x=1/2   $  $   2|x-2|+|2-x|=15   $ leftrightarrow 2|x-2|+|-(x-2)|=15$   $ leftrightarrow 2|x-2|+|x-2|=15$   $ leftrightarrow 3|x-2|=15$   $ leftrightarrow |x-2|=5$   $ leftrightarrow  left[  begin{array}{l}x-2=5  x-2=-5 end{array}  right.$   $ leftrightarrow  left[  begin{array}{l}x=7  x=-3 end{array}  right.$   Vậy x in{-3;7}