\(=3ab^2\)

\(\sqrt{3^2a^2b^4}\)=3a\(b^2\)

\(\sqrt{\dfrac{45\left(x+y\right)^2.y^2}{16}}\left(dkxd:x\ge0,y\ge0\right)\\ =\dfrac{\sqrt{45\left(x+y\right)^2.y^2}}{\sqrt{16}}\\ =\dfrac{\sqrt{45}.\sqrt{\left(x+y\right)^2}.\sqrt{y^2}}{\sqrt{4^2}}\\ =\dfrac{\sqrt{3^2.5}.\left|x+y\right|.\left|y\right|}{4}\\ =\dfrac{3\sqrt{5}\left(x+y\right).y}{4}\\ =\dfrac{3\sqrt{5}\left(xy+y^2\right)}{4}\)

x^ 3 mà

y^3 nhầm

48 y 4 = 16 . 3 y 4 = 4 . y 2 3

8 y 2 = 4 . 2 y 2 = 2 y 2 = - 2 y 2 ( với y < 0 )

√(28a4b2 ) = √((2a2b)2.7) = √7 |2a2b| = 2√7a2b (do b ≥ 0)

25 x 3 = 25 x 2 . x = 5 x x = 5 x x ( với x > 0 )

7 x 2 = x 7 = x 7 ( với x > 0 )

\(\sqrt{\left(-9\right)\cdot\left(-36\right)\cdot ab^2}\)

\(=\sqrt{9\cdot36\cdot ab^2}\)

\(=3\cdot4\cdot\left|b\right|\cdot\sqrt{a}\)

\(=12\left|b\right|\cdot\sqrt{a}\)