Question

1.2:thực hiện phép tính(tính nhanh nếu có thể )

i) (84.34-21.64):(42.9)

1.4: tìm x

a)\(\left(3x-2^4\right).7^3=2.7^4\)

Answer 1

1.4:

a: =>3x-16=2*7=14

=>3x=30

=>x=10

1.3:

\(=\dfrac{21\left(4\cdot34-64\right)}{42\cdot9}=\dfrac{1}{2}\cdot\dfrac{4\left(34-16\right)}{9}=\dfrac{1}{2}\cdot4\cdot2=4\)

Answer 2

`@` `\text {Answer}`

`\downarrow`

`i)`

`(84*34-21*64) \div (42*9)`

`= (21*4 * 34 - 21 * 4* 16) \div (42 * 9)`

`= 84*(34 - 16) \div (42*9)`

`= 84*18 \div 42*9`

`= 1512 \div 378`

`= 4`

`1.4`

`a)`

`(3x - 2^4) * 7^3 = 2*7^4`

`=> (3x - 2^4) = 2*7^4 \div 7^3`

`=> (3x-2^4) = 2*7`

`=> 3x - 2^4 = 14`

`=> 3x = 14 + 2^4`

`=> 3x = 30`

`=> x = 30 \div 3`

`=> x = 10`

Vậy, `x = 10.`