Bài1 :tìm x
a) 7/5×x+3/7=-4/5
B) |x|+0,573=2
C)|x+1/3|-4=-1
Bài 2:tìm số nguyên a
A) -3/7 { "@context": "https://schema.org", "@type": "QAPage", "mainEntity": { "@type": "Question", "name": " Bài1 :tìm x
a) 7/5×x+3/7=-4/5
B) |x|+0,573=2
C)|x+1/3|-4=-1
Bài 2:tìm số nguyên a
A) -3/7
Giải thích các bước giải:
Bài 1:
a) $\dfrac{7}{5} \times x + \dfrac{3}{7}=\dfrac{-4}{5}\\⇔ \dfrac{7}{5} \times x = \dfrac{-4}{5}-\dfrac{3}{7}\\⇔ \dfrac{7}{5} \times x = \dfrac{-43}{35}\\⇔ x = \dfrac{-43}{35}: \dfrac{7}{5}\\⇔x = \dfrac{-43}{49}$
b) $|x|+0,573=2\\⇔|x|=2-0,573\\⇔|x|=1,427\\⇔ x = \pm 1,427$
c) $\bigg|x+\dfrac{1}{3}\bigg|-4=-1\\⇔\bigg|x+\dfrac{1}{3}\bigg|=3\\⇔\left[ \begin{array}{l}x+\dfrac{1}{3}=3\\x+\dfrac{1}{3}=-3\end{array} \right.\\ ⇔\left[ \begin{array}{l}x=3 – \dfrac{1}{3}\\x=-3-\dfrac{1}{3}\end{array} \right.\\⇔ \left[ \begin{array}{l}x=\dfrac{8}{3}\\x=\dfrac{-10}{3}\end{array} \right.$
Vậy `x ∈ {8/3; (-10)/3}`
Bài 2:
a) $\dfrac{-3}{7} < \dfrac{a}{5}<\dfrac{1}{4}\\⇔ \dfrac{-60}{140}<\dfrac{28a}{140}<\dfrac{35}{140}\\⇔ -60 < 28a<35\\⇔ \dfrac{-15}{7} < a < 1,25\\ \Rightarrow a \in \{ -2; -1; 0;1\}$
b) $\dfrac{2}{5}<\dfrac{3}{a}<\dfrac{1}{2}\\ ⇔ \dfrac{6}{15}< \dfrac{6}{2a}<\dfrac{6}{12}\\⇔ 15 > 2a>12\\⇔ 7,5>a>6\\⇔ a = 7$
Bài1 :Tìm x
a) 7/5 × x + 3/7 = -4/5
7/5 × x = -4/5 – 3/7
7/5 × x = -43/35
b) |x| + 0,573 = 2
|x| + = 2 – 0,573
|x| + = 1,427
=> x = 1,427 ; -1,427
c) |x+1/3| – 4 = -1
|x+1/3| = -1 + 4
|x+1/3| = 3
=> x = -10/3 ; 8/3