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3579 - ( 49 - 5 + 3579 ) + 49
= 3579 - 49 + 5 - 3579 + 49
= ( 3579 - 3579 ) + ( 49 - 49 ) + 5
= 0 + 0 + 5
= 5
9) -48725 - ( 357 - 48725 ) + 300
= - 48725 + ( - 357) + 48725 + 300
= [ ( - 48725 ) + 48725 ] + [ ( - 357) + 300]
= 0 + ( -57)
= - 57
10) 3579 - ( 49 - 5 + 3579 ) + 49
= 3579 + ( -49) + 5 + ( -3579) +49
= [ 3579 + ( -3579) ] + [ ( - 49) + 49] + 5
= 0 + 0 + 5
= 5
9) - 48275 - ( 357 - 48725 ) + 300
= -48275 - 357 + 48725 + 300
= ( - 48725 + 48725 ) + ( -357 + 300)
= -57
10) 3579- ( 49 - 5 + 3579 ) + 49
= 3579 - 49 + 5 - 3579 + 49
= ( 3579 - 3579) + (-49 + 49) + 5
= 0+0+5= 5
\(a.35-17+1993-35-1993\\ =-17+\left(35-35\right)+\left(1993-1993\right)\\ =-17+0+0\\ =-17\\ b.-48725-\left(357-48725\right)+300\\ =-48725-357+48725+300\\ =\left(300-357\right)+\left(48725-48725\right)\\ =-57+0\\ =-57\\ c.3579-\left(49-5+3579\right)+49\\ =3579-49+5-3579+49\\ =5+\left(3579-3579\right)+\left(49-49\right)\\ =5+0+0\\ =5\)
a) \(35-17+1993-35-1993\)
\(=\left(35-35\right)+\left(1993-1993\right)-17\)
\(=-17\)
b) \(-48725-\left(357-48725\right)+300\)
\(=\left(-48725+48725\right)+\left(300-357\right)\)
\(=-57\)
c) \(3579-\left(49-5+3579\right)+49\)
\(=\left(3579-3579\right)+\left(49-49\right)+5\)
\(=5\)
(14568+3579)-(14563+3564)
= 14568+3579-14563-3564
=(14568-14563)+(3579-3564)
=5+15=20
Ta có : 1-2+3-4+5-6+7-...-48+49-50
=(1-2)+(3-4)+(5-6)+...+(49-50)
=(-1)+(-1)+(-1)+...+(-1)
=(-1)*25
=-25
1-2+3-4+5-6+7-....-48+49-50
=(1-2)+(3-4)+(5-6)+(7-8)+.....+(47-48)+(49-50) có 25 cặp số như thế
= -1 + -1 + -1 + -1 +.....+ -1 + -1
= -1 x 25
= -25
a) \(\left(-25\right).5.\left(-4\right).2\)
\(=\left[\left(-25\right).\left(-4\right)\right].\left(2.5\right)\)
\(=100.10=1000\)
b) \(\left(-456\right)-\left(67-456\right)\)
\(=-456-67+456\)
\(=\left(456-456\right)-67\)
\(=67\)
\(B=1.2.3+2.3.4+3.4.5+.......+49.50.51\)
\(\Rightarrow4B=1.2.3.4+2.3.4.4+3.4.5.4+.......+49.50.51.4\)
\(=1.2.3.4+2.3.4\left(5-1\right)+3.4.5\left(6-2\right)+.........+49.50.51.\left(52-48\right)\)
\(=1.2.3.4+2.3.4.5-1.2.3.4+3.4.5.6-2.3.4.5+.........+49.50.51.52-48.49.50.51\)
\(=49.50.51.52\)
\(\Rightarrow B=\frac{49.50.51.52}{4}=1624350\)
=3579-49+5-3579+49
=(3579-3579)+(-49+49)+5
=0+0+5
=5
3579 - (49 - 5 + 3579) + 49
= 3579 - 49 + 5 - 3579 + 49
= (3579 - 3579) - (49 - 49) + 5
= 0 - 0 + 5
= 0 + 5
= 5