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a) x ∈ {-2;-1;;0;1;2;3}
b) x ∈ {10;11;12}
c) x ∈ {0;1;2;3;4;5}
d) x ∈ {-1;0;1;2}
a) $420-(71+420)$
$=420-71-420$
$=-71$
b) $(35-120)+(120+410-35)$
$=35-120+120+410-35$
$=(35-35)+(-120+120)+410$
$=410$
c) $(320-15+49)-(85-51)$
$=320-15+49-85+51$
$=320+(-15-85)+(49+51)$
$=320+(-100)+100$
$=320$
d) $-(312+59)-(41+400+88)$
$=-312-59-41-400-88$
$=(-312-88)+(-59-41)-400$
$=-400+(-100)-400$
$=-500-400$
$=-900$
e) $(430-731)-(-731+430-56)$
$=430-731+731-430+56$
$=(430-430)+(-731+731)+56$
$=56$
f) $(1352-47)-(53-1000+1352)$
$=1352-47-53+1000-1352$
$=(1352-1352)+(-47-53)+1000$
$=(-100)+1000$
$=1000-100$
$=900$
h) $(-42)-(370+58)-(120-370)$
$=-42-370-58-120+370$
$=(-42-58)+(-370+370)-120$
$=-100-120$
$=-220$
$Toru$
\(\frac{1}{2}+\frac{5}{6}+\frac{11}{12}+\frac{19}{20}+...+\frac{89}{90}\)
\(=1-\frac{1}{2}+1-\frac{1}{6}+1-\frac{1}{12}+1-\frac{1}{20}+...+1-\frac{1}{90}\)
\(=9-\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{90}\right)\)
\(=9-\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{9.10}\right)\)
\(=9-\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+....+\frac{1}{9}-\frac{1}{10}\right)\)
\(=9-\left(1-\frac{1}{10}\right)\)
\(=9-\frac{9}{10}=\frac{81}{10}\)
S = 1 - 17/6 + 31/12 - 49/20 + 71/30 - 97/42 + 127/56 - 161/72 + 199/90
S = (1 - 17/6) + (31/12 - 49/20) + (71/30 - 97/42) + (127/56 - 161/72) + 199/90
S = -11/6+2/15+2/35+2/63+199/90
S = 3/5
a)(201-111+29)-(-119+230)
=(201-111+29)+119-230
=119+119-230
=8
b)567+[(-99)+41]+(-708)
=567+(-58)+(-708)
=-199
c)[171+(-159)-[-183-(-195)]
=171+(-159)-[-183+195]
=171+(-195)-12
=-36
d)(225+135)+90-[315+(-685)]
=360+90-(-370)
=820
\(\frac{5}{6}+\frac{11}{12}+\frac{19}{20}+...+\frac{89}{90}\)
\(=1-\frac{1}{6}+1-\frac{1}{12}+1-\frac{1}{20}+...+1-\frac{1}{90}\)
\(=8-\left(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{90}\right)\)
\(=8-\left(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{9.10}\right)\)
\(=8-\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+....+\frac{1}{9}-\frac{1}{10}\right)\)
\(=8-\left(\frac{1}{2}-\frac{1}{10}\right)\)
\(=\frac{38}{5}\)
789. 2- 56+ (-95)+111+261+498-215+49+1236-4591-56+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
= 1578- 56+ (-95)+111+261+498-215+49+1236-4591-56+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=1522+ (-95)+111+261+498-215+49+1236-4591-56+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=1427+111+261+498-215+49+1236-4591-56+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=1538+261+498-215+49+1236-4591-56+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=1799+498-215+49+1236-4591-56+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=2297-215+49+1236-4591-56+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=2082+49+1236-4591-56+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=2131+1236-4591-56+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=3367-4591-56+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=-1224-56+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=-1280+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=2909+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=2957+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=3009-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=2009-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=1509+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=1739+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=34239-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=28639+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=31280+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=32133+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=32328-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=31764+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=31999+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=36186+9023177-5000000+562+159-90+459-420+562+235+489+71+12
=9059363-5000000+562+159-90+459-420+562+235+489+71+12
=4059363+562+159-90+459-420+562+235+489+71+12
=4059925+159-90+459-420+562+235+489+71+12
=4060084-90+459-420+562+235+489+71+12
=4059994+459-420+562+235+489+71+12
=4060453-420+562+235+489+71+12
=4060033+562+235+489+71+12
=4060595+235+489+71+12
=4060830+489+71+12
=4061319+71+12=4061402
ủa:q. rảnh v:))