Midterm 3: Version C Answer Key
[latexpage]
- \(\dfrac{\cancel{15}3\cancel{m^3}}{4\cancel{n^2}}\cdot \dfrac{\cancel{17}\cancel{n^3}}{\cancel{30}\cancel{10}2\cancel{m^3}}\cdot \dfrac{\cancel{3}1m^4}{\cancel{34}2n^{\cancel{2}}}\Rightarrow \dfrac{3m^4}{16n}\)
- \(\dfrac{5v^2-25v}{5v+25}\cdot \dfrac{10v}{v^2-11v+30}\Rightarrow \dfrac{\cancel{5}v\cancel{(v-5)}}{\cancel{5}(v+5)}\cdot \dfrac{10v}{\cancel{(v-5)}(v-6)}\Rightarrow \dfrac{10v^2}{(v+5)(v-6)}\)
- \(\phantom{1}\)
\(\left(\dfrac{8}{2x}=\dfrac{2}{x}+1\right)(2x) \\ \)
\(\begin{array}{rrl}
8&=&2\cdot 2+1(2x) \\
8&=&\phantom{-}4+2x \\
-4&&-4 \\
\midrule
\dfrac{4}{2}&=&\dfrac{2x}{2} \\ \\
x&=&2
\end{array}\) - \(\begin{array}{l}
\dfrac{\left(\dfrac{x^2}{y^2}-16\right)y^3}{\left(\dfrac{x+4y}{y^3}\right)y^3}\Rightarrow \dfrac{x^2y-16y^3}{x+4y}\Rightarrow \dfrac{y(x^2-16y^2)}{x+4y}\Rightarrow\dfrac{y(x-4y)\cancel{(x+4y)}}{\cancel{x+4y}} \\ \\
\Rightarrow y(x-4y)
\end{array}\) - \(\begin{array}{l}
\\
5y+2\cdot 9y+6y\sqrt{y} \\
23y+6y\sqrt{y}
\end{array}\) - \(\dfrac{(28)(7+3\sqrt{5})}{(7-3\sqrt{5})(7+3\sqrt{5})}\Rightarrow \dfrac{196+84\sqrt{5}}{49-9\cdot 5}\Rightarrow \dfrac{196+84\sqrt{5}}{4}\Rightarrow 49+21\sqrt{5}\)
- \(\begin{array}{l}
\\ \\ \\ \\ \\ \\ \\
(27a^{-\frac{3}{8}})^{\frac{1}{3}} \\ \\
27^{\frac{1}{3}}a^{-\frac{3}{8}\cdot \frac{1}{3}} \\ \\
3a^{-\frac{1}{8}} \\ \\
\dfrac{3}{a^{\frac{1}{8}}}\Rightarrow \dfrac{3}{\sqrt[8]{a}}
\end{array}\) - \(\phantom{1}\)
\((\sqrt{3x-2})^2=(\sqrt{5x+4})^2 \\ \)
\(\begin{array}{rrrrrrrr}
&3x&-&2&=&5x&+&4 \\
-&3x&-&4&&-3x&-&4 \\
\midrule
&&&-6&=&2x&& \\ \\
&&&x&=&\dfrac{-6}{2}&=&-3
\end{array}\) - \(\phantom{1}\)
- \(\begin{array}{rrl}
\\ \\ \\
\dfrac{2x^2}{2}&=&\dfrac{72}{2} \\ \\
x^2&=&36 \\
x&=&\pm 6
\end{array}\) - \(\begin{array}{rrl}
\\ \\
2x^2-8x&=&0 \\
2x(x-4)&=&0 \\
x&=&0, 4
\end{array}\)
- \(\begin{array}{rrl}
- \(\phantom{1}\)
- \(\begin{array}{rrl}
\\
(x+5)(x+1)&=&0 \\
x&=&-1, -5
\end{array}\) - \(\begin{array}{l}
\\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\
\text{Quadratic:} \\ \\
x^2-10x+4=0 \\ \\
\dfrac{-(-10)\pm \sqrt{(-10)^2-4(1)(4)}}{2} \\ \\
\dfrac{-10\pm \sqrt{100-16}}{2} \\ \\
\dfrac{10\pm \sqrt{84}}{2} \\ \\
\dfrac{10\pm 2\sqrt{21}}{2}\Rightarrow 5 \pm \sqrt{21}
\end{array}\)
- \(\begin{array}{rrl}
- \(\phantom{1}\)
\(\left(\dfrac{8}{4x}=\dfrac{2}{x}+3\right)(4x) \\ \)
\(\begin{array}{rrrrl}
8&=&8&+&3(4x) \\
-8&&-8&& \\
\midrule
\dfrac{0}{12}&=&\dfrac{12x}{12}&& \\ \\
x&=&0&&\therefore \text{Undefined. No solution}
\end{array}\) - \(\begin{array}{rrl}
\\ \\ \\ \\ \\ \\ \\
\text{Let }u&=&x^2 \\ \\
u^2-17u+16&=&0 \\
(u-16)(u-1)&=&0 \\ \\
(x^2-16)(x^2-1)&=&0 \\
(x-4)(x+4)(x-1)(x+1)&=&0 \\
x&=& \pm 1, \pm 4
\end{array}\) - \(\begin{array}{ll}
\begin{array}{rrl}
\\ \\ \\ \\
L&=&W+6 \\
\text{Area}&=&12+\text{Perimeter} \\ \\
L\cdot W&=& 12+2L+2W \\
(W+6)W&=&12+2(W+6)+2W \\
W^2+6W&=&12+2W+12+2W
\end{array}
& \hspace{0.25in}
\begin{array}{rrrrcrr}
\\ \\ \\ \\ \\ \\ \\
0&=&W^2&+&6W&& \\
&&&-&4W&-&24 \\
\midrule
0&=&W^2&+&2W&-&24 \\
0&=&(W&+&6)(W&-&4) \\
W&=&\cancel{-6},&4&&& \\ \\
L&=&W&+&6&& \\
L&=&4&+&6&& \\
L&=&10&&&& \\
\end{array}
\end{array}\) - \(\phantom{1}\)
\(x, x+2, x+4 \\ \)
\(\begin{array}{ll}
\begin{array}{rrrrrrrrrrr}
&&x(x&+&4)&=&31&+&x&+&2 \\
x^2&+&4x&&&=&33&+&x&& \\
&-&x&-&33&&-33&-&x&& \\
\midrule
x^2&+&3x&-&33&=&0&&&&
\end{array}
& \hspace{0.25in}
\begin{array}{l}
\dfrac{-b\pm \sqrt{b^2-4ac}}{2a} \\ \\
\dfrac{-3\pm \sqrt{3^2-4(1)(-33)}}{2} \\ \\
\dfrac{-3\pm \sqrt{141}}{2}
\end{array}
\end{array}\) - \(\begin{array}{rrrrcl}
\\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\
&d&=&r&\cdot &t \\
\text{To outpost:}&60&=&(B&-&C)5 \\
\text{Back:}&60&=&(B&+&C)3 \\ \\
&60&=&5B&-&5C \\
&60&=&3B&+&3C \\ \\
&12&=&B&-&C \\
+&20&=&B&+&C \\
\midrule
&32&=&2B&& \\
&\therefore B&=&16&\text{ km/h}& \\ \\
&\therefore B&+&C&=&\phantom{-}20 \\
&16&+&C&=&\phantom{-}20 \\
-&16&&&&-16 \\
\midrule
&&&C&=&4\text{ km/h}
\end{array}\)