a) Ta có: CD//Ey

\(\Rightarrow\widehat{CBE}=\widehat{E_1}=130^0\)(so le trong)

b) Ta có: Ta có: CD//Ey

\(\Rightarrow\widehat{EBD}+\widehat{E_1}=180^0\)(trong cùng phía)

\(\Rightarrow\widehat{EBD}=180^0-\widehat{E_1}=50^0\)

Ta có: \(\widehat{EBD}+\widehat{B_1}=50^0+40^0=90^0\)

=> AB⊥BE

\(49x^2-4=0\)

\(\Rightarrow49x^2=4\)

\(\Rightarrow x^2=\dfrac{4}{49}\)

\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{2}{7}\\x=-\dfrac{2}{7}\end{matrix}\right.\)