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222-9+11+12:2*14+14 = ? ( )

## 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

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)

1. Giải đáp:
1) – 39
2)  – 12
3) 0
4) – 100
5)  400
6) – 50
Lời giải và giải thích chi tiết:
1) ( 768 – 39 ) – 768
= 768 – 39 – 768
= ( 768 – 768 ) – 39
= – 39
2) ( – 1579 )  – ( 12 – 1579 )
= – 1579 – 12 + 1579
= ( – 1579 + 1579 ) – 12
= 0 – 12
= – 12
3) 324 + [ 112 – ( 112 + 324 )]
= 324 + ( 112 – 112 – 324 )
= 324 + ( – 324 )
= 0
4) ( – 257 ) – [ ( 156 – 257 ) – 56 ]
= – 257 – ( 156 – 257 – 56 )
= – 257 – 156 + 257 + 56
= – ( 257 – 257 ) – ( 156 – 56 )
= – 100
5) ( 27 + 65 ) + ( 335 – 27 )
= 27 + 65 + 335 – 27
= ( 27 – 27 ) + ( 335 + 65 )
= 400
6) ( 42 – 69 ) – ( 42 – 19 )
= 42 – 69 – 42 + 19
= ( 42 – 42 ) – ( 69 – 19 )
= – 50

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