Bài 1.3 : Tìm x, biết : a, 2|3x – 1|+ 1= 5 b, |x/2 – 1| = 3 c, |-x + 2/5| + 1/2 = 3,5 d, |x – 1/3| = 2/1/5

Question

Bài 1.3 : Tìm x, biết :
a, 2|3x – 1|+ 1= 5
b, |x/2 – 1| = 3
c, |-x + 2/5| + 1/2 = 3,5
d, |x – 1/3| = 2/1/5

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4 years 2020-11-03T21:32:43+00:00 1 Answers 292 views 0

1. Đáp án:

a) x=1 hoặc x=-1/3

b) x=8 hoặc x=-4

c) x=-13/5 hoặc x=17/5

d) x=38/15 hoặc x=-28/15

Giải thích các bước giải:

a) 2|3x-1|+1=5

⇔2|3x-1|=4

⇔|3x-1|=2

⇔$$\left[ \begin{array}{l}3x-1=2\\3x-1=-2\end{array} \right.$$

⇔$$\left[ \begin{array}{l}3x=3\\3x=-1\end{array} \right.$$

⇔$$\left[ \begin{array}{l}x=1\\x=-1/3\end{array} \right.$$

vậy x=1 hoặc x=-1/3

b) |x/2-1|=3

⇔$$\left[ \begin{array}{l}x/2-1=3\\x/2-1=-3\end{array} \right.$$

⇔$$\left[ \begin{array}{l}x/2=4\\x/2=-2\end{array} \right.$$

⇔$$\left[ \begin{array}{l}x=8\\x=-4\end{array} \right.$$

vậy x=8 hoặc x=-4

c) |2/5-x|+1/2=3,5

⇔|2/5-x|=7/2-1/2

⇔|2/5-x|=3

⇔$$\left[ \begin{array}{l}2/5-x=3\\2/5-x=-3\end{array} \right.$$

⇔$$\left[ \begin{array}{l}x=2/5-3\\x=2/5+3\end{array} \right.$$

⇔$$\left[ \begin{array}{l}x=-13/5\\x=17/5\end{array} \right.$$

vậy x=-13/5 hoặc x=17/5

d) |x-1/3|=2“1/5

⇔|x-1/3|=11/5

⇔$$\left[ \begin{array}{l}x-1/3=11/5\\x-1/3=-11/5\end{array} \right.$$

⇔$$\left[ \begin{array}{l}x=11/5+1/3\\x=-11/5+1/3\end{array} \right.$$

⇔$$\left[ \begin{array}{l}x=38/15\\x=-28/15\end{array} \right.$$

vậy x=38/15 hoặc x=-28/15