1: 243^5=(3^5)^5=3^25

3*27^8=3*(3^3)^8=3^25

=>243^5=3*27^8

6: 125^5=(5^3)^5=5^15

25^7=(5^2)^7=5^14

=>125^5>25^7(15>14)

5: 78^12-78^11=78^11(78-1)=78^11*77

78^11-78^10=78^10*77

mà 11>10

nên 78^12-78^11>78^11-78^10

1: 243^5=(3^5)^5=3^25

3*27^8=3*3^24=3^25=243^5

3: 3^300=27^100

2^200=4^100

mà 27>4

nên 3^300>2^200

4: 15^2=3^2*5^2

81^3*125^3=3^12*5^9

=>15^2<81^3*125^3

6: 125^5=5^15

25^7=5^14

mà 15>14

nên 125^5>25^7

\(B=72\times74=\left(73-1\right)\left(73+1\right)=73^2+73-73-1=73^2-1< 73^2=73\times73=A\)

\(B=\left(73-1\right)\left(73+1\right)=73^2-1< 73^2=A\)

Câu 1:

A = 72^45 - 72^44 = 72^44.(72 - 1) = 72^44.71

B = 72^44 - 72^43 = 72^43.(72 - 1) = 72^43.71

A > B

Câu 2:

A = 78^12 - 78^11 và B = 78^11 - 78^10

A = 78^12.(78 - 1) = 78^12.77

B = 78^11 - 78^10 = 78^10.(78 - 1) = 78^10.77

A > B

sao lại không thực hiện phép tính chứ ? 

các tổng đều bằng nhau

32+74+96+18+50=90+36+12+54+78=10+52+76+94+38=98+14+30+72+56

23,45<34,99;102,567>102,49

99,78>99,12;78,56=78,560

Bài 2,

3,45;4,3;5,6;5,9;102,609

Bài 1: 99,78 < 99,12  ; 78,56 > 78,560

Bài 2:

102,609 > 5,9 > 5,6 > 4,3 > 3,45

c: \(78\cdot31+78\cdot24+78\cdot17+72\cdot22\)

\(=78\cdot\left(31+24+17\right)+72\cdot22\)

\(=72\cdot78+72\cdot22=72\cdot100=7200\)

d: \(\left(456\cdot11+912\right)\cdot37:13:74\)

\(=\frac{456\left(11+2\right)}{13}\cdot\frac{37}{74}=456\cdot\frac12=\frac{456}{2}=228\)

e: [\(\left(315+372\right)\cdot3+\left(372+315\right)\cdot7\) ]:\(\left(26\cdot13+74\cdot14\right)\)

\(=687\cdot\left(3+7\right):\left\lbrack26\cdot13+74\cdot13+74\right\rbrack\)

=687*10:[1300+74]

=687*10:1374

=5

Tham khảo: