Question

Đơn giản biểu thức

a) - ( 35 - x ) - ( y - 40 )

b) 4 . ( x - 3 ) - ( 2x + 18 )

2. Tính nhanh

a) - ( 314 - 25 ) - ( 27 - 75 ) - 73

b) ( -56 . 77 . 90 ) : [ -8 . 72 . ( -45 ) ]

Answer 1

Bài 1:

a/

- (35 - x) - (y - 40) = -35 + x - y + 40

= (x - y) + [(-35) + 40) = x - y + 5

b/ 4 . (x - 3) - (2x + 18)

= (4x - 4.3) - (2x + 18)

= 4x - 12 - 2x - 18 = 4x - 2x + [(-12)+(-18)]

= 2x - 30

Bài 2:

a/ -(314 - 25) - (27 - 75) - 73

= - 314 + 25 - 27 + 75 - 73

= -314 + {(25 + 75) + [(-27) - 73]}

= -314 + (100 - 100) = -314 + 0 = -314

b/ (-56 . 77 . 90) : [-8 . 72 . (-45)]

= [-56 : (-8)] . (77 : 72) . [90 : (-45)]

= 7 . \(\frac{77}{72}\)\(\frac{77}{72}\).(-2) = -14 . \(\frac{77}{72}\) = \(\frac{-539}{36}\)