a) 42.50 – 38.50 – 25.4 = 50.(42 – 38) – 25.4 = 50.4 – 25.4 = (50 – 25).4 = 25.4 = 100

b) 32.38 + 17.94 – 15.38 – 32.17 = 38.(32 – 15) + (94 – 32).17 = 38.17 + 62.17 = 17.(38+62) = 17.100 = 1700

Mn giúp e vs ạ, em chuẩn bị phải nộp bài rùi T - T

\(a,=27\cdot20+73\cdot20-27=20\left(27+73\right)-27\\ =20\cdot100-27=2000-27=1973\\ b,=42\cdot50-38\cdot50-50\cdot2=50\left(42-38-2\right)=50\cdot2=100\\ e,=254\left(58+21\cdot2\right)=254\cdot100=25400\\ c,=53\left(12+172-84\right)=53\cdot100=5300\\ d,=24\left(31+42+27\right)=24\cdot100=2400\\ f,=\left(9-8-...-1\right)\left(500\cdot9-500\cdot9\right)=\left(9-8-...-1\right)\cdot0=0\)

a. 27*(20-1)+73*20=27*20-27+73*20=20*(27+73)-27=20*100-27=2000-27=1973

b. =42*50-38*50-50*2=50*(42-38-2)=50*2=100

C. =53*(12+172-84)=53*100=5300

D.=31*24+24*42+24*27=24*(31+42+27)=24*100=2400

E.=508*29+21*508=508*(29+21)=508*50=25400

21,30 +45,21 +42 ,50 =  66, 51 + 42,50

                                      =109,01

k nha ! 

=21.30+21.45+2.21.50

=21.(30+45+2+50)

=21.127

=2667

21,30 + 45,21 + 42,50 = 66,51 + 42,50 

                                       = 109,01

\(\left(-79\right).\left(8-313\right)-313.79\)

\(=-79.\left(8-313+313\right)\)

\(=-79.8\)

\(=-632\)

\(32.17.\left(-125\right).25.2\)

\(=32.25.\left(-125\right).2.17\)

\(=800.\left(-250\right).17\)

\(=200000.17\)

\(=3400000\)

học tốt

a) = (50-1)^2 = 50^2 - 2.50 + 1 = 2500 - 100 + 1 = 2401

b) = (50+1)^2 = 50^2 + 2.50 + 1 = 2601

c) = 9900

a) \(52^2\)

\(=\left(50+2\right)^2\)

\(=50^2+2\cdot2\cdot50+2^2\)

\(=2500+200+4\)

\(=2704\)

b) \(98^2\)

\(=\left(100-2\right)^2\)

\(=100^2-2\cdot100\cdot2+2^2\)

\(=10000-400+4\)

\(=9604\)

`a, 52^2 = (50+2)^2 = 2500 + 200 + 4 = 2704`

`b, 98^2  = (100-2)^2 = 100^2 - 2 . 100 . 2 + 4 = 10000 - 400 + 4`

`= 9604`

\(a,9\times435\times4+12\times565\times3\)

\(=36\times435+36\times565\)

\(=36\times\left(435+565\right)\)

\(=36\times1000\)

\(=36000\)

\(b,4\times1368\times21-7\times368\times12\)

\(=84\times1368-84\times368\)

\(=84\times\left(1368-368\right)\)

\(=84\times1000\)

\(=84000\)

TL

$a)9\times 435\times 4+12\times 565\times 3$

$=36\times 435+36\times 565$

$=36\times \left(435+565\right)$

$=36\times 1000$

$=36000$

$b)4\times 1368\times 21-7\times 368\times 12$

$=84\times 1368-84\times 368$

$=84\times \left(1368-368\right)$

$=84\times 1000$

$=84000$

$HT$

a. 2.54

b. 0.5