Question

Tính tổng :

a) 25 + (–17) –15

b) (–20) + (–7)

c) S₁ = 1+ (–2) + 3 + (–4) +…+ 2001 + (–2002)

d) S₂ = 1+ (–3) + 3 + (–7) +…+ 1999 + (–2002)

e) S₃ = 1+ (–2) + (–3)+ 4+5+(–6)+( –7)+8+…+1997+(–1998)+( –1999)+2000

f) (325 – 47)+(175 – 53)

g) (756 – 217) – (183 – 44)

h) (–2104) – 2015 + 2016

mai nộp rồi

Answer 1

a) 25 + (–17) –15

=(25-15)-(17)

=10-(-17)

=-7

b) (–20) + (–7)= (-13)

c) S₁ = 1+ (–2) + 3 + (–4) +…+ 2001 + (–2002)

=1-2+3-4+...+2001-2002

=(1-2)+(3-4)+.....(2001-2002)

=(-1)+(-1)+....(-1)

=[(2002-1):1+1]:2=1001

=(-1).1001

=(-1001)

d) S₂ = 1+ (–3) + 3 + (–7) +…+ 1999 + (–2002)

e) S₃ = 1+ (–2) + (–3)+ 4+5+(–6)+( –7)+8+…+1997+(–1998)+( –1999)+2000

=1+2-3-4+5+6-7-8+...+1997+1998-1999-2000

=(1+2-3-4)+(5+6-7-8)+...(1997+1998-1999-2000)

=(-4)+(-4)+...+(-4)

=2000:4=500

=(-4).500

=(-2000)

f) (325 – 47)+(175 – 53)

=325+47+175-53

=(325+175)-(47+53)

=500-100

=400

g) (756 – 217) – (183 – 44)

=756+217-183+44

=(756+44)-(183+217)

=800-400 mình ko biết câu d

Answer 2

a)25+(-17)-15=25-15+(-17)

=10+(-17)

=-7

b)(-20)+(-7)=-27
c)S1=1+(-2)+3+(-4)+...+2001+(-2002)

S1=-1+(-1)+...+(-1)

S1=-1.1001

S1=-1001

e)1+(-2)+(-3)+4+5+(-6)+(-7)+8+...+1997+(-1998)+(-1999)+2000

=[1+(-2)+(-3)+4]+[5+(-6)+(-7)+8]+...+[1997+(-1998)+(-1999)+200]
=0+0+...+0

=0

f)(325-47)+(175-53)

=325-47+175-53

=(325+175)+(-47-53)

=500+(-100)

=400

g)(756-217)-(183-44)

=756-217-183+44

=(756+44)-(217+183)

=800+400

=1200

h)(-2104)-2015+2016

=-4119+2016

=-2103