How to solve the problems related to exponents in precalculus



In this post we are going to show how to solve exponent forms in precalculus ,first of all we should know the formulas that we are going to use while solving problems in  exponents, 

you can click here to check which formulas we are going to use in these questions. lets start

\(\bullet \;\; \displaystyle \frac{2^{10}}{2^3}\)

SOLUTION: we know that \(\displaystyle \frac{a^m}{a^n} =a^{m-n} \;\;\;\) so we are going to use this here

here \(\;\;a= 2\) lets take \(\;\;m =10 ,n =3\) so by ules of exponent we have

\(\displaystyle \frac{2^{10}}{2^3}=2^{10-3}=2^7\)




\(\bullet\;\; \displaystyle \frac{5^{10} \times 2^{5}}{5^{6} \times 2^4}\)

SOLUTION: Above expression can also be written as

\( \;\; \displaystyle \frac{5^{10} \times 2^{5}}{5^{6} \times 2^4 }= \frac{5^{10}}{5^{6}} \times \frac{2^{5}}{2^4}\)

again using rules of exponents we get

\( \displaystyle \frac{5^{10}}{5^{6}} \times \frac{2^{5}}{2^4}= 5^{10-6} \times 2^{5-4}=5^{4}\times2^{1}\)

ANSWER: \(5^{4} \times 2\)



\(\bullet \;\; \displaystyle \frac{4^{5}}{4^3}\)

SOLUTION:

Above Expression can be written as

\( \displaystyle \frac{4^{5}}{4^3}= 4^{5-3}\;=\; 4^{2}\;\;\;\; \cdots\cdots 1\)

\(\text{and we know that}\;\)\(\;\; 4=2^2\) so we will use this in (1)

\(\Rightarrow \displaystyle 4^{2}\;=\; (2^2)^{2}\)

\(\Rightarrow (2^2)^{2}\;=\;2^{2 \times 2}\)

\(\Rightarrow 2^{2 \times 2} \;=\; 2^4\)

ANSWER: \(\;\;2^4 \;\;\textbf{or} \;\;16\)



\(\bullet \;\; \displaystyle \frac{2^5 \times 10^{2}}{4^2 \times 25}\)

SOLUTION:

Above Expression can be written as

\(\Rightarrow\displaystyle \frac{2^5 \times 10^{2}}{4^2 \times 25} = \frac{2^5 \times (2\times 5)^{2}}{(2^2)^2 \times 5^{2}}\)

\(\Rightarrow\displaystyle \frac{2^5 \times (2\times 5)^{2}}{(2^2)^2 \times 5^{2}} = \frac{2^5 \times 2^{2}\times 5^{2}}{2^4 \times 5^{2}}\)

\(\Rightarrow\displaystyle \frac{2^5 \times 2^{2}\times 5^{2}}{2^4 \times 5^{2}} = \frac{2^{5+2} \times 5^{2}}{2^4 \times 5^{2}}\)

\(\Rightarrow\displaystyle \frac{2^{5+2} \times 5^{2}}{2^4 \times 5^{2}} = \frac{2^{7} \times 5^{2}}{2^4 \times 5^{2}}\)

\(\Rightarrow\displaystyle \frac{2^{7} \times 5^{2}}{2^4 \times 5^{2}} = \frac{2^{7}}{2^4} \times \frac{5^{2}}{5^{2}}\)

\(\Rightarrow\displaystyle \frac{2^{7}}{2^4} \times \frac{5^{2}}{5^{2}} = 2^{7-4} \times {5^{2-2}}\)

\(\Rightarrow\displaystyle 2^{7-4} \times {5^{2-2}} = 2^{3} \times {5^{0}}\)

\(\text{we know that}\)\(\;\; a^{0} =1 \;, a \neq 0 \) using this we can write above equation as

\(\Rightarrow\displaystyle 2^{3} \times {5^{0}}=8\times 1\)

ANSWER: \(\;\;8 \)




\(\bullet \;\; \displaystyle \frac{2^2 \times 3^{2}}{18^2 \times 3^5\times 5^2}\)

SOLUTION:

Above Expression can be written as

\( \displaystyle \frac{2^2 \times 3^{2}}{18^2 \times 3^5\times 5^2}=\frac{2^2 \times 3^{2}}{(2 \times 9)^2 \times 3^5\times 5^2}\)

\(\Rightarrow\displaystyle\frac{2^2 \times 3^{2}}{(2 \times 3^2)^2 \times 3^5\times 5^2}\)

\(\Rightarrow\displaystyle \frac{2^2 \times 3^{2}}{2^2 \times (3^2)^2 \times 3^5\times 5^2}\)

\(\Rightarrow\displaystyle \frac{2^2 \times 3^{2}}{2^2 \times 3^4 \times 3^5\times 5^2}\)

\(\Rightarrow\displaystyle  \frac{2^2 \times 3^{2}}{2^2 \times 3^{4+5} \times 5^2}\)

\(\Rightarrow\displaystyle \frac{2^2 \times 3^{2}}{2^2 \times 3^{9} \times 5^2}\)

now above expression can be written as

\(\Rightarrow\displaystyle \frac{2^2}{2^2} \times \frac{3^2}{3^9}\times \frac{1}{5^2}\)

\(\Rightarrow\displaystyle \frac{2^{2-2} \times 3^{2-9} }{5^2}\)

\(\Rightarrow\displaystyle  \frac{2^{0}\times 3^{-7}}{5^2}\)

\(\Rightarrow\displaystyle  \frac{2^{0}\times 3^{-7}}{5^2}\)

We know form exponents formulas \(\;\; \displaystyle a^{-m}=\frac{1}{a^m} \) or \(\displaystyle\;\;a^m = \frac{1}{a^{-m}}\)

We will use above,So we will get

\(\Rightarrow \displaystyle  \frac{1}{3^7 \times 5^2}\)

ANSWER: \(\;\; \displaystyle \frac{1}{ 3^{7}\times {5^2}}\)



\(\bullet \;\; \displaystyle (-2)^5 \times (-3)^{10}\)


SOLUTION: we can write given expression as

\((-2)^5 \times (-3)^{10}=(-1 \times 2)^5 \times (-1 \times 3)^{10}\)

\(\Rightarrow \displaystyle (-1)^5 \times (2)^5 \times (-1)^{10} \times (3)^{10} \;\;\;\cdots \cdots (1) \)

We have rule that
\(\;\;(-1)^n = \begin{cases} -1 & \text{n is odd} \\ 1 & \text{n is even} \end{cases}\)

So form above rule (1) will become

\(\Rightarrow \displaystyle (-1) \times 2^5 \times 1 \times 3^{10} \)

\(\Rightarrow \displaystyle -2^5 \times 3^{10} \)

ANSWER: \(\;\; -2^5 \times 3^{10}\)




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