\(7ab\cdot\sqrt{\dfrac{36a^4}{49b^2}}\\ =>7ab\cdot\sqrt{\left(\dfrac{6a^2}{7b}\right)^2}\\ =>7ab\cdot\dfrac{6a^2}{7b}\\ =>\dfrac{7ab\cdot6a^2}{7b}\\ =>6a^3\)

\(A=7ab.\sqrt{\dfrac{36a^4}{49b^2}}\)

\(=7ab.\dfrac{6a^2}{\left|7b\right|}\)

\(=7ab.\dfrac{6a^2}{7b}\left(vib>0\right)\)

\(=6a^3\)

Đề là gì bạn?

\(=\left(6a^2-y\right)\left(6a^2+y\right)\)

`a)sqrt{(sqrt7-4)^2}+sqrt7`

`=|sqrt7-4|+sqrt7`

`=4-sqrt7+sqrt7=4`

`b)\sqrt{81a}-sqrt{144a}+sqrt{36a}(a>=0)`

`=9sqrta-12sqrta+6sqrta=3sqrta`

a) Ta có: \(\sqrt{\left(\sqrt{7}-4\right)^2}+\sqrt{7}\)

\(=4-\sqrt{7}+\sqrt{7}\)

=4

b) Ta có: \(\sqrt{81a}-\sqrt{144a}+\sqrt{36a}\)

\(=9\sqrt{a}-12\sqrt{a}+6\sqrt{a}\)

\(=3\sqrt{a}\)

a) \(36a^4-y^2=\left(6a^2-y\right)\left(6a^2+y\right)\)

b) \(6x^2+x-2=2x\left(3x+2\right)-1\left(3x+2\right)=\left(3x+2\right)\left(2x-1\right)\)

1 B

2 C

\(4a^4b-24a^3b^2+36a^2b^3\)

\(=4a^2b\left(a^2-6ab+9b^2\right)\)

\(=4a^2b\left[a^2-2.a.3b+3b^2\right]\)

\(=4a^2b\left(a-3b\right)^2\)

\(4a^4b-24a^3b^2+36a^2b^3\)

\(=4a^2b\left(a^2-6ab+9b^2\right)\)

\(=4a^2b\left[a^2-2\cdot a\cdot3b+\left(3b\right)^2\right]\)

\(=4a^2b\left(a-3b\right)^2\)

   4a⁴b - 24a³b² + 36a²b³

= 4a²b * ( a² - 6ab + 9b² )

= 4a²b * ( a - 3b ) ²

4a²b² + 36a²b³ + 6ab⁴

= 2ab²(2a + 18ab + 3b²)

4a²b³ - 6a³b²

= 2a²b²(2b - 3a)