Toán tìm x biết a,|x-2|=3 b,|x-3|-7=13 c,-12(x-5)+7(3-x)=5 07/12/2021 By Ayla tìm x biết a,|x-2|=3 b,|x-3|-7=13 c,-12(x-5)+7(3-x)=5
a) |x – 2| = 3 => x – 2 = 3 hoặc -3 TH1 : x – 2 = 3 x = 3 + 2 = 5 TH2 : x – 2 = -3 x = -3 + 2 = -1 b) |x – 3| – 7 = 13 |x – 3| = 13 + 7 |x – 3| = 20 => x – 3 = 20 hoặc -20 TH1 : x – 3 = 20 x = 20 + 3 = 23 TH2 : x – 3 = -29 x = -29 + 3 = -26 c) -12(x – 5) + 7(3 – x) = 5 -12x – (-60) + 21 – 7x = 5 -12x + 60 + 21 – 7x = 5 (-12x – 9x) + 60 + 21 = 5 -21x + 81 = 5 -21x = 5 – 81 -21x = -76 x = -76/-21 x = 76/21 Trả lời
a, |x-2|=3 ⇔\(\left[ \begin{array}{l}x-2=3\\x-2=-3\end{array} \right.\)⇔\(\left[ \begin{array}{l}x=5\\x=-1\end{array} \right.\) Vậy x=5 hoặc x=-1 b, |x-3|-7=13 ⇔|x-3|=20 ⇔\(\left[ \begin{array}{l}x-3=20\\x-3=-20\end{array} \right.\)⇔\(\left[ \begin{array}{l}x=23\\x=-17\end{array} \right.\) Vậy x=23 hoặc x=-17 c, -12(x-5)+7(3-x)=5 ⇔-12x+60+21-7x=5 ⇔-12x-7x=5-60-21 ⇔-19x=-76 ⇔x=4 Vậy x=4. Trả lời
a) |x – 2| = 3
=> x – 2 = 3 hoặc -3
TH1 :
x – 2 = 3
x = 3 + 2 = 5
TH2 :
x – 2 = -3
x = -3 + 2 = -1
b) |x – 3| – 7 = 13
|x – 3| = 13 + 7
|x – 3| = 20
=> x – 3 = 20 hoặc -20
TH1 :
x – 3 = 20
x = 20 + 3 = 23
TH2 :
x – 3 = -29
x = -29 + 3 = -26
c) -12(x – 5) + 7(3 – x) = 5
-12x – (-60) + 21 – 7x = 5
-12x + 60 + 21 – 7x = 5
(-12x – 9x) + 60 + 21 = 5
-21x + 81 = 5
-21x = 5 – 81
-21x = -76
x = -76/-21
x = 76/21
a, |x-2|=3
⇔\(\left[ \begin{array}{l}x-2=3\\x-2=-3\end{array} \right.\)⇔\(\left[ \begin{array}{l}x=5\\x=-1\end{array} \right.\)
Vậy x=5 hoặc x=-1
b, |x-3|-7=13
⇔|x-3|=20
⇔\(\left[ \begin{array}{l}x-3=20\\x-3=-20\end{array} \right.\)⇔\(\left[ \begin{array}{l}x=23\\x=-17\end{array} \right.\)
Vậy x=23 hoặc x=-17
c, -12(x-5)+7(3-x)=5
⇔-12x+60+21-7x=5
⇔-12x-7x=5-60-21
⇔-19x=-76
⇔x=4
Vậy x=4.