Đáp án:
Giải thích các bước giải:
c,72 - 3x=5x + 8
⇔ - 3x - 5x=8 - 72
⇔ - 8x=- 64
⇔ x=8
Vậy x=8
d,|x|=3
⇔\(\left[ \begin{array}{l}x=3\\x=-3\end{array} \right.\)
Vậy x ∈ {3;-3}
e,|x - 7|=9
⇔\(\left[ \begin{array}{l}x - 7=9 \\x - 7=-9\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=16\\x=-2\end{array} \right.\)
Vậy x ∈ {16;-2}
f,3.|x - 7|=21
⇔|x - 7|=7
⇔\(\left[ \begin{array}{l}x - 7=7 \\x - 7=-7\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=14\\x=0\end{array} \right.\)
Vậy x ∈ {14;0}
g,-7.|x + 3|=-49
⇔|x - 7|=7
⇔\(\left[ \begin{array}{l}x - 7=7 \\x - 7=-7\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=14\\x=0\end{array} \right.\)
Vậy x ∈ {14;0}
h,2x - 7=x + 9
⇔2x - x=9 + 7
⇔x=16
Vậy x=16
i,2.|x - 3|=6
⇔|x - 3|=3
⇔\(\left[ \begin{array}{l}x - 3=3 \\x - 3=-3\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=6\\x=0\end{array} \right.\)
Vậy x ∈ {6;0}
j,7x - 85=95 + x
⇔7x - x=95 + 85
⇔6x=180
⇔x=30
Vậy x=30
k,8x - x - 75=-x + 15
⇔7x - 75=-x + 15
⇔7x + x=15 + 75
⇔8x =90
⇔ x=45/4
Vậy x=45/4
h,-3.|x - 3|=-9
⇔|x - 3|=3
⇔\(\left[ \begin{array}{l}x - 3=3 \\x - 3=-3\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=6\\x=0\end{array} \right.\)
Vậy x ∈ {6;0}
