Toán Lớp 6: Tính hợp lí:
1) (768 -39)-768
2) (-1579) -(12 -1579)
3) 324 + [112 -(112 + 324)]
4) (-257) -[(156 -257) -56]
5) (27+65) + (335-27)
6) (42 -69)-(42 -19)
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Toán Lớp 6: Tính hợp lí:
1) (768 -39)-768
2) (-1579) -(12 -1579)
3) 324 + [112 -(112 + 324)]
4) (-257) -[(156 -257) -56]
5) (27+65) + (335-27)
6) (42 -69)-(42 -19)
Comments ( 2 )
Đáp án:
1)1) −39-39
2)2) −12-12
3)3) 00
4)4) −100-100
5)5) 400400
6)6) −50-50
Giải thích các bước giải:
1)1) (768−39)−768(768-39)-768
=768−39−768=768-39-768
=(768−768)−39=(768-768)-39
=−39=-39
2)2) (−1579) −(12−1579)(-1579) -(12-1579)
=−1579−12+1579=-1579-12+1579
=(−1579+1579)−12=(-1579+1579)-12
=0−12=0-12
=−12=-12
3)3) 324+[112−(112+324)]324+[112-(112+324)]
=324+(112−112−324)=324+(112-112-324)
=324+(−324)=324+(-324)
=0=0
4)4) (−257)−[(156−257)−56](-257)-[(156-257)-56]
=−257−(156−257−56)=-257-(156-257-56)
=−257−156+257+56=-257-156+257+56
=−(257−257)−(156−56)=-(257-257)-(156-56)
=−100=-100
5)5) (27+65)+(335−27)(27+65)+(335-27)
=27+65+335−27=27+65+335-27
=(27−27)+(335+65)=(27-27)+(335+65)
=400=400
6)6) (42−69)−(42−19)(42-69)-(42-19)
=42−69−42+19=42-69-42+19
=(42−42)−(69−19)=(42-42)-(69-19)
=−50