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Which expression is equivalent to [tex]$3 \sqrt{2 y^3} \cdot 7 \sqrt{18 y}$[/tex], if [tex]$y \ \textgreater \ 0$[/tex]?

A. [tex]$21 y \sqrt{20 y}$[/tex]
B. [tex][tex]$21 y^2 \sqrt{6 y}$[/tex][/tex]
C. [tex]$63 y \sqrt{2 y}$[/tex]
D. [tex]$126 y^2$[/tex]


Sagot :

Certainly! Let's simplify the expression [tex]\(3 \sqrt{2 y^3} \cdot 7 \sqrt{18 y}\)[/tex].

1. Simplify each square root separately.

- First, simplify [tex]\(\sqrt{2 y^3}\)[/tex]:
[tex]\[ \sqrt{2 y^3} = \sqrt{2 y^2 \cdot y} = \sqrt{2 y^2} \cdot \sqrt{y} = y \sqrt{2} \cdot \sqrt{y} = y \sqrt{2 y} \][/tex]

- Next, simplify [tex]\(\sqrt{18 y}\)[/tex]:
[tex]\[ \sqrt{18 y} = \sqrt{9 \cdot 2 y} = \sqrt{9} \cdot \sqrt{2 y} = 3 \sqrt{2 y} \][/tex]

2. Substitute the simplified forms back into the expression:

[tex]\[ 3 \sqrt{2 y^3} \cdot 7 \sqrt{18 y} = 3 (y \sqrt{2 y}) \cdot 7 (3 \sqrt{2 y}) \][/tex]

3. Combine the constants and the terms involving [tex]\(y\)[/tex] and [tex]\(\sqrt{2 y}\)[/tex]:

- Constants: [tex]\(3 \cdot 7 \cdot 3 = 63\)[/tex]
- Terms involving [tex]\(y\)[/tex] and [tex]\(\sqrt{2 y}\)[/tex]:

[tex]\[ \sqrt{2 y} \cdot \sqrt{2 y} = \sqrt{4 y^2} = 2 y \][/tex]

4. Put it all together:

[tex]\[ 63 \cdot y \cdot 2 y = 63 \cdot 2 y^2 = 126 y^2 \][/tex]

Thus, the equivalent expression to [tex]\(3 \sqrt{2 y^3} \cdot 7 \sqrt{18 y}\)[/tex] is [tex]\(126 y^2\)[/tex].

The correct answer is \(D. 126 y^2)\