a, (27+65)+(346-27-65)
=27+65+346-27-65
=92+346-27-65
=438-27-65
=411-65
=346
b, (42-69+17)-(42+17)
=42-69+17+(-42)-17
=[42+(-42)]+[17+(-17)]-69
=0+0-69
=0-69
=-69
mk nhanh nhật tk mk nhé
78. Bỏ dấu ngoặc rồi tính:
a) (27 + 65) + (346 - 27 - 65); b) (42 - 69 + 17) - (42 + 17).
Bài giải:
a) (27 + 65) + (346 - 27 - 65) = 27 + 65 + 346 - 27 - 65
= 27 - 27 + 65 - 65 + 346 = 346
b) (42 - 69 + 17) - (42 + 17) = 42 - 69 + 17 - 42 - 17
= 42 - 42 + 17 - 17 - 69 = -69
a) (27 + 65) + (346 - 27 - 65)
=(27-27)+(65-65)+346
=346
b) (42 - 69 + 17) - (42 + 17)
=42-69+17-42-17
=(42-42)+(17-17)-69
=(-69)
t tôi nhé bn
b) (42 - 69 + 17) - (42 + 17)
= 42 - 69 + 17 - 42 + 17
= (42 - 42) + (17 - 17) + 69
= 0 + 0 + 69
= 69
a,
=27+65+346-27-65
= 92+346-27-65
=438-27-65
= 411-65
=346
a,27+65+346-27-65 b,42-69+17-42+17
= 92 + 319 - 65 = -27 + 17 - 42 +17
= 92 + 254 = -10 - 59
= 346 = -69
a) (27 + 65) + (346 - 27 - 65) = 27 + 65 + 346 - 27 - 65
= 27 - 27 + 65 - 65 + 346 = 346.
b) (42 - 69 + 17) - (42 + 17) = 42 - 69 + 17 - 42 - 17
= 42 - 42 + 17 - 17 - 69 = -69.
