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I need help with this practice problem from my trig prep guide ❗️It asks to answer (a) & (b)Put these separately so I know which is which

I need help with this practice problem from my trig prep guide ❗️It asks to answer-example-1
User BrianP
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1 Answer

22 votes
22 votes

Given the expression:


(3x^5-(1)/(9)y^3)^4

Given that Harold uses boinomial theorem to expand the given binomial, let's solve for the following:

• (a). What is the sum in summation notation that he uses the express the expnansion.

Apply the formula:


\sum ^n_(k=0)nCk(a^(n-k)b^k)

Therefore, the sum in summation nottation will be:


\sum ^4_(k=0)(4!)/((4-k)!k!)\cdot(3x^5)^(4-k)\cdot(-(1)/(9)y^3)^k

• (b). Write the simplified terms of the expansion.

To write the simplified terms, we have:


\begin{gathered} (4!)/(4-0)!0!)*(3x^5)^(4-0)\cdot(-(1)/(9)y^3)^0+(4!)/((4-1)!1!)\cdot(3x^5)^(4-1)\cdot(-(1)/(9)y^3)^1+(4!)/((4-2)!2!)\cdot(3x^5)^(4-2)\cdot(-(1)/(9)y^3)^2+(4!)/((4-3)!3!)\cdot(3x^5)^(4-3)\cdot(-(1)/(9)y^3)^3+(4!)/((4-4)!4!)\cdot(3x^5)^(4-4)\cdot(-(1)/(9)y^3)^4 \\ \\ \\ 81x^(20)-12x^(15)y^3+(2x^(10)y^6)/(3)-(4x^5y^9)/(243)+(y^(12))/(6561) \end{gathered}

ANSWER:


\begin{gathered} (a)\text{. }\sum ^4_(k=0)(4!)/((4-k)!k!)\cdot(3x^5)^(4-k)\cdot(-(1)/(9)y^3)^k \\ \\ \\ (b)\text{. }81x^(20)-12x^(15)y^3+(2x^(10)y^6)/(3)-(4x^5y^9)/(243)+(y^(12))/(6561) \end{gathered}

User Matt Sugden
by
2.7k points
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