Toán Lớp 6: Tìm x |x+2|=9 |x+2|-9 (x+2)^2=9

Question

Toán Lớp 6:  Tìm x |x+2|=9 |x+2|-9 (x+2)^2=9

tuyethutanhthu · Answer

Lời giải và giải thích chi tiết:

a) |x+2|=9

=>\(\left[ \begin{array}{l}x+2=9\\x+2=-9\end{array} \right.\)
=>\(\left[ \begin{array}{l}x=9-2\\x=-9-2\end{array} \right.\)
=>\(\left[ \begin{array}{l}x=7\\x=-11\end{array} \right.\)
Vậy x in {7;-11}

b)

|x+2|=9

=>\(\left[ \begin{array}{l}x+2=9\\x+2=-9\end{array} \right.\)
=>\(\left[ \begin{array}{l}x=9-2\\x=-9-2\end{array} \right.\)
=>\(\left[ \begin{array}{l}x=7\\x=-11\end{array} \right.\)

c)

(x+2)^2=9
=>(x+2)^2=3^2hoặc (x+2)^2=(-3)^2
x+2=3 x+2=(-3)
x=3-2 x=-3-2
x=-1 x=-5
Vậy x in{-1;-5}

haianhtu97 · Answer

a) |x + 2| = 9     &rArr; x + 2 &isin; {-9; 9}     &rArr; x &isin; {-11; 7}     b)      |x + 2| = 9     &rArr; x + 2 &isin; {9; -9}     &rArr; x &isin; {7; -11}     c)      (x + 2)^2 = 9     &rArr; x + 2 &isin; {-3; 3}     &rArr; x &isin; {-5; 1}