a) 42 - x = 5

x = 42 - 5

x = 37

b) 15.(x + 4) = 75

x + 4 = 75 : 15

x + 4 = 5

x = 5 - 4

x = 1

d) x + 18 = 12

x = 12 - 18

x = -6

e) 2x - 15 = -19

2x = (-19) + 15

2x = -4

x = -4 : 2

x = -2

f) 36 : (x^3 - 12) = -3

x^3 - 12 = 36 : (-3)

x^3 - 12 = -12

x^3 = 0

=> x = 0

g)x + 15 = 35

x = 35 - 15

x = 20

h) 2x - 13 = 3^2

2x - 13 = 9

2x = 9 + 13

2x = 22

x = 22 : 2

x = 11

a) 42-x=5

         x=42-5

         x= 37

b)15*(x+4)=75

        x+4=75:15

        x+4=5

        x    =5-4

       x     = 1

12⁸.9¹²=(2².3)⁸.(3²)¹²=2¹⁶.3⁸.3²⁴=2¹⁶.3³²=2¹⁶.(3²)¹⁶=2¹⁶.9¹⁶=(2.9)¹⁶=18¹⁶

=>12⁸.9¹²=18¹⁶

A=4

 câu C mh ko biết, xin lỗi nha

\(12^8.9^{12}=\left(2^2.3\right)^8.\left(3^2\right)^{12}=2^{16}.3^8.3^{24}=2^{16}.3^{32}=2^{16}.\left(3^2\right)^{16}=2^{16}.9^{16}=18^{16}\)

\(12^8.9^{12}=4^8.3^8.9^{12}=2^{16}.9^4.9^{12}=2^{16}.9^{16}=\left(2.9\right)^{16}=18^{16}\left(đpcm\right)\)

\(12^8.9^{12}=(3.2^2)^8.(3^2)^{12}\)

\(=3^8.2^{16}.3^{24}=2^{16}.3^{8+24}=2^{16}.3^{32}\)

\(=2^{16}.9^{16}=(2.9)^{16}=18^{16}\)

\(12^8.9^{12}=3^8.\left(2^2\right)^8.9^{12}=9^4.2^{16}.9^{12}=2^{16}.9^{16}=\left(2.9\right)^{16}=18^{16}\)

nên bạn ghi thiếu đề nha, 18¹⁶ mới đúng

Ta có:+, 12^8. 9^12 = (12^2)^4. (3^3)^4

                             =144^4. 27^4       

                             = 3888^4

           +, 18^16 = (18^4)^4

                         = 104976^4

           Vì 3888^4 < 104976^4 nên 12^8. 9^12< 18^16

                                Vậy 12^8 . 9^12 < 18^16

a)=(-14).(-5)
=70
b)=(32-2):(-5)
=30:(-5)
=-6
c)=-72-12
=-84
d)=-35+(-4)-39
=-39-39
=-78
e)=78:(-30+36)
=78:6
=13
f)=-3.(-3)-12
=9-12
=-3
g)=45-5-2+12
=40-2+12
=38+12
=50

mình giải luôn chứ mik hông chép đề đâu nha^^

a) (-6 - 8) . (-9 + 4)

= (-14) . (-5)

= 70.

b) (8. 4 - 2) : (-5)

= (32 - 2) : (-5)

= 30 : (-5)

= -6.

c) -8. 9 - (-9 + 21)

= -8. 9 - 12

= -72 - 12

= -84.

d) -5. 7 + (-32) : 8 - (-15 + 54)

= -5. 7 + (-32) : 8 - 39

= -35 + (-32) : 8 - 39

= -35 + (-4) - 39

= -39 - 39

= -78.

e) 78 : (-6. 5 + 36)

= 78 : (-30 + 36)

= 78 : 6

= 13.

f) 15 : (-5). (-3) - 12

= -3. (-3) - 12

= 9 - 12

= -3.

g) 45 - 15 : +3 - 18 : 6 + 12

= 45 - 5 - 18 : 6 + 12

= 45 - 5 - 3 + 12

= 40 - 3 + 12

= 37 + 12

= 49.