\(\left(5x^2-2x+1\right)\left(2x^2-3x\right)=10x^4-15x^3-4x^3+6x^2+2x^2-3x\)

\(=10x^4-19x^3+8x^2-3x\)

\(3\cdot5^2-16:2^2=3\cdot25-16:4=75-4=71\)

3.5² - 16 : 2²

= 3 . 25 - 16 : 4

= 75 - 4 = 71

các bạn giải giúp mình nhé

\(=\dfrac{1}{11}-\dfrac{1}{11}+\dfrac{1}{41152}=\dfrac{1}{41152}\)

\(\dfrac{3}{5}+\dfrac{13}{25}-\dfrac{5}{9}-\dfrac{3}{7}\)

\(=\dfrac{15}{25}+\dfrac{13}{25}-\dfrac{35}{63}-\dfrac{27}{63}\)

\(=\dfrac{28}{25}-\dfrac{62}{63}=\dfrac{214}{1575}\)

bằng 214/1575

`a)3/5+13/5-5/9-3/7`

`=16/5-5/9-3/7`

`=698/315`

3/5 + 13 /5 -5/9 - 3/7 = 698/315

Bài 3:

a)3.5²-16:2²=71

b)15.141+59.15=15(141+59)=3000

c)2³.17-2³.14=2³(17-14)=8.3=24

(câu b hình như thiếu dấu "+"?)

a) 71

b) 24

c) 3000

Tick cho mình.

a)3.5²-16:2²

= 3. 25 - 16 :4

= 75 - 4

= 71

b)15.141+59.15

= 15.(141+59)

= 15. 200

= 3000

c)2³.17-2³.14

= 2³ .(17-14)

= 8 . 3

= 24

a. `17.85+15.17-120`

`=17 . (85+15)-120`

`=17 . 100-120`

`=1700-120`

`=1580`

b. `5.7^2 - 24 : 2^3`

`=5. 49 - 24: 8`

`=245-3`

`=242`

c. `3^3 .22 -27.19`

`=27.22 - 27.19`

`=27 . (22-19)`

`=27.3=81`

a = 1580

b = 242

c = 81

a. 17.85 + 15.17 - 120

=17(85+15)-120

=17.100-120

=1700-120

=1580

b. 5.7² - 24:2³ 

=5.49-24:8

=245-3

=242

c. 3³.22 - 27.19

=27.22-27.19

=27(22-19)

=81

1.3200 : 40 . 2 = 80 . 2 =160

 2,3920:28:2= 70

 3.....=12

a: \(3200:40\cdot2=160\)

b: \(3920:28:2=70\)

c: \(\left(3^4\cdot5^7-9^2\cdot21\right):3^5=3^2\cdot5^7-7=703118\)

Dạng tổng quát: \(\dfrac{a+b}{ab}=\dfrac{1}{a}+\dfrac{1}{b}\)

Áp dụng:

\(A=\dfrac{3}{1.2}-\dfrac{5}{2.3}+\dfrac{7}{3.4}-...+\dfrac{15}{7.8}-\dfrac{17}{8.9}\)

\(=\left(1+\dfrac{1}{2}\right)-\left(\dfrac{1}{2}+\dfrac{1}{3}\right)+\left(\dfrac{1}{3}+\dfrac{1}{4}\right)-...+\left(\dfrac{1}{7}+\dfrac{1}{8}\right)-\left(\dfrac{1}{8}+\dfrac{1}{9}\right)\)

\(=1+\dfrac{1}{2}-\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}+\dfrac{1}{4}-...+\dfrac{1}{7}+\dfrac{1}{8}-\dfrac{1}{8}-\dfrac{1}{9}\)

\(1-\dfrac{1}{9}=\dfrac{8}{9}\)