Tính nhanh
a) -(-892+1977)+(-1892-1023)
b) -99.81+99.31-99.50
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Lời giải:
a. $=(36+76)-89-(44+56)$
$=112-89-100=12-89=-(89-12)=-77$
b. $=342-567-642+767-458$
$=(342-642)+(767-567)-458=-300+200-458=-100-458=-(100+458)=-558$
c. $=1892-892+852-300-852$
$=(1892-892)+(852-852)-300=1000+0-300=700$
d.
$=472-281-513-372+181-487$
$=(472-372)-(281-181)-(513+487)$
$=100-100-1000=-1000$
e.
$=912-1268-812+1368-100$
$=(912-812)+(1368-1268)-100=100+100-100=100$
a) ( 100 – 1 ) 3 = 970299. b) ( 91 + 9 ) 3 = 100 3 .
c) ( 1000 + 1 ) 3 = 1003003001. d) ( 102 – 2 ) 3 = 100 3 .
a: \(2004^2-16\)
\(=\left(2004-4\right)\left(2004+4\right)=2000\cdot2008=4016000\)
b: \(892^2+892\cdot216+108^2\)
\(=892^2+2\cdot892\cdot108+108^2\)
\(=\left(892+108\right)^2=1000^2=1000000\)
c: \(36^2+26^2-52\cdot36\)
\(=36^2-2\cdot36\cdot26+26^2\)
\(=\left(36-26\right)^2=10^2=100\)
d: \(\left(10,2\cdot9,8-9,8\cdot0,2\right)+\left(10,22-10,2\cdot0,2\right)\)
\(=9,8\left(10,2-0,2\right)+10,22-2,04\)
=98+8,18
=106,18
e: \(20,03\cdot45+20,03\cdot47+20,03\cdot8\)
\(=20,03\cdot\left(45+47+8\right)\)
\(=20,03\cdot100=2003\)
g: \(15,75\cdot175-15,75\cdot55-15,75\cdot20\)
\(=15,75\cdot\left(175-55-20\right)\)
\(=15,75\cdot100=1575\)
h: \(A=57^2+114\cdot43+43^2\)
\(=57^2+2\cdot57\cdot43+43^2\)
\(=\left(57+43\right)^2=100^2=10000\)
i: \(B=5^4\cdot3^4-\left(15^2-1\right)\left(15^2+1\right)\)
\(=15^4-\left(15^4-1\right)=1\)
k: \(C=50^2-49^2+48^2-47^2+\cdots+2^2-1^2\)
\(=\left(50-49\right)\left(50+49\right)+\left(48-47\right)\left(48+47\right)+\cdots+\left(2-1\right)\left(2+1\right)\)
=50+49+...+2+1
\(=50\cdot\frac{51}{2}=25\cdot51=1225\)
a: \(2004^2-16=2000\cdot2008=4016000\)
b: \(892^2+892\cdot216+108^2=1000^2=1000000\)
c: \(36^2-52\cdot36+26^2=10^2=100\)
\(M=896+892+888+...+24\)
\(M=\frac{\left(896+24\right).219}{2}=100740\)
\(N=18.21+21+21.79\)
\(N=21.\left(18+1+79\right)=21.100\)
\(N=2100\)
b,
N=18x21+21+21x79
N=18x21+21x1+21x79
N=(18+1+79)x21
N=98x21
N=2058
\(A=\frac{113+892+187+808}{742-23+158-372}\)
\(A=\frac{\left(113+187\right)+\left(892+808\right)}{\left(742-372\right)+\left(158-23\right)}\)
\(A=\frac{300+1700}{370+135}\)
\(A=\frac{2000}{505}=\frac{400}{101}\)
a) -(-892+1977)+(-1892-1023)
\(=892-1977-1892-1023\)
\(=\left(892-1892\right)+\left(-1977-1023\right)\)
\(=\left(-1000\right)+\left(-3000\right)\)
\(=-4000\)
b) -99.81+99.31-99.50
\(=99.\left(-81+31-50\right)\)
\(=99.0=0\)