Question

Bài 2 : Thực hiện phép tính hợp lí

 a] 128 + 43  + 72 + 57

 b] 41 . 51 + 49. 51

 c] 4 mu 7 : 4 mu 5

 d] 2.( 5.4 mu 2 - 18)

 

Answer 1

a) 128 + 43 + 72 + 57

= ( 128 + 72 ) + ( 43 + 57 )

= 200 + 100

= 300

b) 41 . 51 + 49 . 51

= 51 . ( 41 + 49 )

= 51 . 90

= 4590

= 

Answer 2

\(a,\) \(128+43+72+57\)

\(=\left(128+72\right)+\left(43+57\right)\)

\(=200+100\)

\(=300\)

\(b,\) \(41.51+49.51=51.\left(41+49\right)=51.90=4590\)

\(c,\) \(4^7:4^5=4^{7-5}=4^2=16\)

\(d,\) \(2.\left(5.4^2-18\right)\)

\(=2.\left(5.2^4-2.3^2\right)\)

\(=2.2.\left(5.2^3-3^2\right)\)

\(=4.\left(40-9\right)\)

\(=4.31=123\)