Question

tính nhanh : A,  \(\dfrac{7,2:2\cdot28,6+1,43\cdot2\cdot64}{13+5+7+...+49-339}\)

tìm x           : B, 2+( \(\dfrac{3}{2}\)+ x - \(\dfrac{5}{8}\) ) : \(\dfrac{13}{4}\)=6

Answer 1

a: Sửa đề; \(A=\dfrac{7.2:2\cdot28.6+1.43\cdot2\cdot64}{1+3+5+7+...+49-339}\) 

\(=\dfrac{3.6\cdot28.6+2.86\cdot64}{1+3+5+...+49-339}\)

\(=\dfrac{2.86\left(64+36\right)}{25^2-339}=\dfrac{286}{286}=1\)

b: =>2(x+7/8)=6*13/4=78/4=39/2

=>x+7/8=39/4

=>x=71/8