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Mathematics 14 Online
OpenStudy (anonymous):

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OpenStudy (jdoe0001):

\(\bf \sqrt{3x^2}\cdot \sqrt{4x}\implies \sqrt{3x^2\cdot 4x}\implies \sqrt{12x^2}\\ \quad \\ \color{blue}{12\implies 2\times 2\times 3\implies 2^2\times 3}\\ \quad \\ \sqrt{12x^2}\implies \sqrt{2^2\times 3}\)

OpenStudy (jdoe0001):

\(\bf \sqrt{3x^2}\cdot \sqrt{4x}\implies \sqrt{3x^2\cdot 4x}\implies \sqrt{12x^2}\\ \quad \\ \color{blue}{12\implies 2\times 2\times 3\implies 2^2\times 3}\\ \quad \\ \sqrt{12x^2}\implies \sqrt{2^2\times 3\times x^2}\)

OpenStudy (anonymous):

thank you i got C is that correct?

OpenStudy (anonymous):

Not quite, but close.

OpenStudy (anonymous):

Actually jdoe made a mistake, he missed an x at the last step of the first line. it's supposed to be x to the 3rd power

OpenStudy (anonymous):

\[\sqrt{3*x^2*4*x} = \sqrt{12*x^3}\]

OpenStudy (tkhunny):

We keep losing an x. \(\sqrt{3x^{2}}\cdot\sqrt{4x}\) Since we have that x by itself in the second radical, we now know that x is NOT negative!! This is good news. \(\sqrt{3}\sqrt{x^{2}}\cdot\sqrt{4}\sqrt{x}\) Pick off the easy one. \(\sqrt{3}\sqrt{x^{2}}\cdot 2 \sqrt{x}\) We now use the fact that \(x \ge 0\) \(\sqrt{3} \;x\cdot 2 \sqrt{x}\) Rearrange a little: \(2x\sqrt{3}\sqrt{x} = 2x\sqrt{3x}\)

OpenStudy (anonymous):

technically \[2*\left| x \right|*\sqrt{3*x}\]

OpenStudy (tkhunny):

Technically, no. \(\sqrt{x^{2}} = x\) IF you know that \(x \ge 0\), which we do in this case. Had \(\sqrt{4x}\) not appeared separately, we would not have known that. Absolute values are not required in this case.

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