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Mathematics 7 Online
OpenStudy (anonymous):

How do you solve this problem? Please explain!

OpenStudy (anonymous):

\[(4a ^{5/3})^{3/2}\]

OpenStudy (anonymous):

Solve for what?

OpenStudy (anonymous):

It says to simplify in this problem

OpenStudy (irishboy123):

basic rule is \(\large (b^n)^m = b^{n \times m}\) because it's \(b^n \times b^n \times b^n ......\) m times. so \(\large (a. \ b^n)^m = a^m \ . \ b^{n \times m}\) But you can go at this in a number of ways; and you might wish to try this approach: \(\large (4a^{5/3})^{3/2} = \sqrt{4a^{5/3} \ * 4a^{5/3} \ * 4a^{5/3} }\) it's not the immediate solution, you will get that by looking up the exponent rules as posted above, but it might help get you get comfortable with these kind of questions.....maybe under the \(^{3/2}\) umbrella you are cubing and square rooting....

OpenStudy (anonymous):

How would I multiply the numbers inside the square root?

OpenStudy (irishboy123):

well, imagine the square root is not there. jut multiply those out as you normally would: \(4 a^{5/3} \times 4 a^{5/3} \times4 a^{5/3} \) we'll worry about the square root sign after we have done that.

OpenStudy (anonymous):

Okay. When you are multiplying exponents you have to add them right?

OpenStudy (phi):

when multiplying the same base , you add the exponents.

OpenStudy (anonymous):

So without the square root it equals 4a^5?

OpenStudy (phi):

if you remember that x*x*x is x^3 but x is x^1 and x*x is x^2 you get the example x^1 * x^2 = x^3 (that is how I remember this rule)

OpenStudy (phi):

yes, but you also have 4*4*4 to do

OpenStudy (irishboy123):

nah you also have 4 x 4 x 4!!

OpenStudy (anonymous):

64a^5?

OpenStudy (irishboy123):

fine i'll leave it to @phi you are in great hands!! good luck

OpenStudy (anonymous):

then it would equal 8a.....how would I square root the 5?

OpenStudy (phi):

a^5 is a*a*a*a * a we can do square root of a^4 (it is a*a or a^2) square root of the "extra" a is either sqr(a) or a^1/2

OpenStudy (phi):

\[ \sqrt{64 a^4 } \sqrt{a} \]

OpenStudy (anonymous):

So the answer is \[8a \sqrt{a}\]?

OpenStudy (phi):

8a^2 sqr(a)

OpenStudy (anonymous):

So that would be simplified?

OpenStudy (phi):

they probably want you to use exponents, so write sqr(a) as a^(1/2)

OpenStudy (anonymous):

\[8a ^{2}a ^{1/2}\]

OpenStudy (anonymous):

Like that?

OpenStudy (phi):

yes, and though it looks a bit weird, we are multiplying the same base. (the a) so we add the exponents. you get 2.5 but generally people write it as an improper fraction

OpenStudy (anonymous):

Oh okay. Thanks!

OpenStudy (phi):

in other words, 2+ 1/2 is 4/2 + 1/2 = 5/2 and people write \[ 8 a^\frac{5}{2} \]

OpenStudy (anonymous):

Ya I got it. :)

OpenStudy (phi):

if you are doing a lot of this, I would use the "fast way" \[ (b^n)^m = b^{n \cdot m} \] for example \[ (4^1 \cdot a ^\frac{5}{3})^\frac{3}{2} \] becomes \[ 4^\frac{3}{2} \cdot a^{\frac{5}{3}\cdot \frac{3}{2} }\]

OpenStudy (phi):

notice the expoinet of a is 5*3/(3*2) which simplifies to 5/2 to find what 4^3/2 is, we have to do either \[ \left( 4^\frac{1}{2}\right)^3 = 2^3 = 8 \] or \[ \left( 4^3\right)^\frac{1}{2}= 64^\frac{1}{2} = 8 \]

OpenStudy (anonymous):

Oh that makes sense.

OpenStudy (phi):

if it doesn't , doing a dozen problems will be tedious.

OpenStudy (anonymous):

Ya that's true.

OpenStudy (anonymous):

Do you happen to know how to do this problem? How do you make both numbers have the same base? \[(5a ^{2/3})(4a ^{3/2})\]

OpenStudy (phi):

you are multiplying 4 "things" 5* a^(2/3) * 4 * a^(3/2) and you can switch the order: 5*4 * a^(2/3) * a^(3/2) does that help to know how to tackle this ?

OpenStudy (anonymous):

I think so. I got 20 as my final answer.

OpenStudy (phi):

yes 4*5 is 20 but you can't ignore the a's (but you can multiply them using "same base, add exponents" rule)

OpenStudy (anonymous):

Oh ya the a is \[a ^{1}\] So then the final answer would actually be 20a.

OpenStudy (phi):

when you *multiply* (like here) , and you have the same base, you *add* the exponents. in other words you get a^ new exponent and the new exponent is 2/3 + 3/2

OpenStudy (phi):

use a common denominator of 6 to get 4/6 + 9/6

OpenStudy (anonymous):

Oh....I was multiplying them again. So that would equal 13/6.

OpenStudy (phi):

yes. this stuff is confusing but try to remember the x*x = x^2 or (putting in the exponents) \[ x^1 \cdot x^1 = x^2\] as an example of adding the exponents

OpenStudy (anonymous):

Oh okay. So then it would equal \[20a ^{13/6}\]?

OpenStudy (phi):

yes

OpenStudy (anonymous):

Okay thanks again!

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