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Giải hộ mk bài này nx nha!
Cho hình vẽ:
a) kể tên góc nhọn
b) kể tên góc tù
c) kể tên cặp góc kề bù
nhanh nha!
a,\(\frac{1}{3}\),đặt tính ra
b,-1,đặt tính ra
c,x-1#0=>x#1
a)\(\frac{1}{n}-\frac{1}{n+1}=\frac{n+1}{n\left(n+1\right)}-\frac{n}{n\left(n-1\right)}=\frac{n+1-n}{n\left(n+1\right)}=\frac{1}{n\left(n+1\right)}\)
\(\Rightarrow\frac{1}{n\left(n+1\right)}=\frac{1}{n}.\frac{1}{n+1}\)
b) \(C=\frac{1}{2}.\frac{1}{3}+\frac{1}{3}.\frac{1}{4}+\frac{1}{4}.\frac{1}{5}+\frac{1}{5}.\frac{1}{6}+\frac{1}{6}.\frac{1}{7}+\frac{1}{7}.\frac{1}{8}\)
\(=\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}\)
\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}\)
\(=\frac{1}{2}+0+0+0+0+0-\frac{1}{8}\)
\(=\frac{1}{2}-\frac{1}{8}=\frac{4}{8}-\frac{1}{8}=\frac{4-1}{8}=\frac{3}{8}\)
Ta có : \(\frac{\frac{3}{5}+\frac{3}{7}-\frac{1}{3}+\frac{3}{11}}{\frac{6}{5}+\frac{6}{7}-\frac{2}{3}+\frac{6}{11}}=\frac{\frac{3}{5}+\frac{3}{7}-\frac{1}{3}+\frac{3}{11}}{2\left(\frac{3}{5}+\frac{3}{7}-\frac{1}{3}+\frac{3}{11}\right)}=\frac{1}{2}\)
Lại có : \(\frac{\left(\frac{1}{4}-\frac{1}{5}-\frac{1}{20}\right).2021}{\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{99.100}}=\frac{0.2021}{\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{99.100}}=0\)
Khi đó \(B=\frac{1}{2}+0=\frac{1}{2}\)
d) \(\frac{x}{-9}=\left(\frac{2}{6}\right)^2\)
\(\Rightarrow\frac{x}{-9}=\frac{2}{6}.\frac{2}{6}\)
\(\Rightarrow\frac{x}{-9}=\frac{4}{36}\)
\(\Rightarrow\frac{x}{-9}=\frac{1}{9}\)
\(\Rightarrow\frac{-x}{9}=\frac{1}{9}\)
\(\Rightarrow-x=1\)
\(\Rightarrow x=1\)
e) \(\frac{a}{b}+\frac{3}{6}=0\)
\(\Rightarrow\frac{a}{b}=0-\frac{3}{6}\)
\(\Rightarrow\frac{a}{b}=0-\frac{1}{2}\)
\(\Rightarrow\frac{a}{b}=\frac{-1}{2}\)
\(\Rightarrow a=-1;b=2\)