65 - 5 = 60     65 - 60 = 5     65 - 65 = 0

70 - 30 = 40     94 - 3 = 91     33 - 30 = 3

21 - 1 = 20     21 - 20 = 1     32 - 10 = 22

65 - 5 = 60       65 - 60 = 5       65 - 65 = 0

70 - 30 = 40       94 - 3 = 91       33 - 30 = 3

21 - 1 = 20       21 - 20 = 1       32 - 10 = 22

Toán lớp 1 không có cái này đâu !!!

65 - 5 = 60     65 - 60 = 5     65 - 65 = 0

70 - 30 = 40     94 - 3 = 91     33 - 30 = 3

21 - 1 = 20     21 - 20 = 1     32 - 10 = 22

930 x 65 + 65 x 70

= 65 x (930 + 70)

= 65 x 1000

= 65 000

930 x 65 + 65 x 70 = (930 + 70) x 65

= 65000

930 x 65 + 65 x 70

= 65 x (930 + 70)

= 65 x 1 000

= 65 000

\(6\div2\left(1+2\right)\)

\(=6\div2.3\)

\(=3.3\)

\(=9\)

\(6\div2\left(1+2\right)=6\div2.3\\ =6\div6\\ =1 \)

\(6\div2\times\left(1+2\right)=3\times\left(1+2\right)\\ =3\times3\\ =9\)

C=70x(3+9)-12x(65-5)                                                                        C=70x. 12. - 12x. 60.                                                                           C=840-720.                                                                                     C=120

-420-{-50+[-70+65-(54-49)]}

=-420-{-50+[-70+65-54+49]}

=-420-(-50-70+65-54+49)

=-420+50+70-65+54-49

=-360

\(300+500:2\)

\(=300+250\)

\(=550\)

\(300+500\div2\)

\(=300+250\)

\(=550\)

\(300\) \(+\) \(500\) \(:\) \(2\)

\(=\) \(300\) \(+\) \(250\)  

\(=\) \(550\)

\(35\cdot34+70\cdot38+65\cdot75+65\cdot35\)

\(=35\cdot34+35\cdot76+65\cdot\left(75+35\right)\)

\(=35\cdot\left(34+76\right)+65\cdot110\)

\(=35\cdot110+65\cdot110\)

\(=110\cdot\left(65+35\right)\)

\(=110\cdot100=11000\)

35 . 34 + 70 . 38 + 65 . 75 + 65 . 35

= 35 . 34 + 35 . 76 + 65 . 75 + 65 . 35

= 35 . (34 + 76) + 65 . (75 + 35)

= 35 . 110 + 65 . 110

= 110 . (35 + 65)

= 110 . 100

= 11000

~Std well~

\(35\cdot34+70\cdot38+65\cdot75+65\cdot35\)

\(=35\cdot34+35\cdot76+65\cdot75+65\cdot35\)

\(=35\cdot\left(34+76\right)+65\cdot\left(75+35\right)\)

\(=35\cdot110+65\cdot110\)

\(=110\cdot\left(35+65\right)\)

\(=110\cdot100=11000\)

a) Ta có: \(8^n:2^n=16^{2011}\)

\(\Leftrightarrow4^n=\left(4^2\right)^{2011}\)

\(\Leftrightarrow n=4022\)

b) Ta có: \(2^n+2^{n+3}=144\)

\(\Leftrightarrow2^n\left(1+2^3\right)=144\)

\(\Leftrightarrow2^n=16\)

hay n=4

\(8^n\div2^n=16^{2011}\)

\(\left(8\div2\right)^n=\left(4^2\right)^{2011}\)

\(4^n=4^{4022}\)

\(\Rightarrow n=4022\)

mình nghĩ ý b là

\(2^n+2^{n+3}=144\)

\(2^n+2^n\cdot2^3=144\)

\(2^n\left(1+8\right)=144\)

\(2^n\cdot9=144\)

\(2^n=16\)

\(2^n=2^4\)

\(\Rightarrow n=4\)

  50 + 55 + 60 + 65 + 70 + 75 + 80 + 85

= ( 50 + 85 ) + ( 55 + 80 ) + ( 60 + 75 ) + ( 65 + 70 ) ------ ( có 4 cặp số ) 

= 135 x 4 = 540 

Số các số hạng là (85 - 50)/5 + 1 = 8 (số)

Tổng trên là:

8 * (85 + 50) / 2 = 540 

Tui làm mà ko ai thèm tick luôn !!! Híc híc