Question

[nguyen thi yen chi]

tìm x biết

a)\(5\le2.x< 13\)

b)\(5< 4.x+1\le17\)

c)x+1/2+1/6+1/12+1/20+1/30=8

LÀM ƠN NHANH GIÚP MK

Answer 1

[titanic]

a)\(5\le2.x< 13\)''

\(\frac{5}{2}\le x< \frac{13}{2}\)( chia cho 2)

b)\(5< 4.x+1\le17\)

\(5-1< 4x\le17-1\)( trừ cho 1 )

\(4< 4x\le16\)

\(\frac{4}{4}< x\le\frac{16}{4}\)

\(1< x\le4\)

c) \(x+\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}=\frac{1}{8}\)

\(x+\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}=8\)

\(x+1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}=8\)( Áp dụng \(\frac{1}{a.\left(a+1\right)}=\frac{1}{a}-\frac{1}{a+1}\))

\(x+1-\frac{1}{6}=8\)

\(x=8-1+\frac{1}{6}\)

\(x=\frac{43}{6}\)