Question

1.Thực hành phép tính (tính nhanh nếu có thể)

a, 120-5.(20-2.3²)

b, 2⁵:2³-3.3²+5.7

c, 35.(85-47)+85.(47-35)

Giúp mình nhé!!!

Answer 1

a) \(120-5\cdot\left(20-2\cdot3^2\right)\\ =120-5\left(20-2\cdot9\right)\\ =120-5\left(20-18\right)\\ =120-5\cdot2\\ =120-10\\ =110\)

b) \(2^5:2^3-3\cdot3^2+5\cdot7\\ =2^2-3^3+35\\ =4-9+35\\ =\left(-5\right)+35\\ =30\)

c) \(35\cdot\left(85-47\right)+85\cdot\left(47-35\right)\\ =35\cdot85-35\cdot47+85\cdot47-85\cdot35\\ =\left(35\cdot85+85\cdot47\right)-\left(35\cdot47+85\cdot35\right)\\ =85\left(35+47\right)-35\left(47+85\right)\\ =85\cdot82-35\cdot132\\ =6970-4620\\ =2350\)

Answer 2

b) 2⁵ : 2³ - 3 . 3² + 5 . 7

= 2² - 3³ + 35

= 4 - 27 + 35

= -23 + 35

= 12

Answer 3

c) 35. ( 85 - 47 ) + 85. ( 47 - 35 )

= 35 . 85 - 35 . 47 + 85 . 47 - 85 . 35

= ( 35 . 85 - 85 . 35 ) - 47 . ( 35 - 85 )

= 0 - 47 . (-50)

= -2350