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  1. simplify -2(2x+3)+6x-9
  2. solve for t 1/2+2/5t-1=1/5t+t
 Apr 17, 2015

Best Answer 

 #3
avatar+118667 
+11

Hi Zac,

 

Thanks for answering these questions :)

 

There is a couple of things here.

 

1) I think it should be       $$10t^2+5t-2=0\qquad (NOT -5t)$$

 

2) I am not sure what the asker INTENDED the question to be BUT this was the question.

 

1/2+2/5t-1=1/5t+t

 

Technically this should be interpreted as

$$\\\frac{1}{2}+\frac{2}{5}t-1=\frac{1}{5}t+t\\\\
\frac{1}{2}+\frac{2t}{5}-1=\frac{1t}{5}+t\qquad $The t is on the top$\\\\
\frac{-1}{2}+\frac{2t}{5}=\frac{6t}{5}\\\\
\frac{-1}{2}=\frac{4t}{5}\\\\
\frac{-1*5}{2*4}=t\\\\
t=\frac{-5}{8}\\\\$$

 

Also, I would like you to consider putting in some blank lines.  

Sometimes mine is spread out too much, I realize that, but I personally find it a bit hard to read when there are no spaces.  This may just be a peronal preference.  I am not sure :/

 Apr 18, 2015
 #1
avatar+980 
+8

1.

$${\mathtt{\,-\,}}{\mathtt{2}}{\mathtt{\,\times\,}}\left({\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{x}}{\mathtt{\,\small\textbf+\,}}{\mathtt{3}}\right){\mathtt{\,\small\textbf+\,}}{\mathtt{6}}{\mathtt{\,\times\,}}{\mathtt{x}}{\mathtt{\,-\,}}{\mathtt{9}}$$

$${\mathtt{\,-\,}}{\mathtt{4}}{\mathtt{\,\times\,}}{\mathtt{x}}{\mathtt{\,-\,}}{\mathtt{6}}{\mathtt{\,\small\textbf+\,}}{\mathtt{6}}{\mathtt{\,\times\,}}{\mathtt{x}}{\mathtt{\,-\,}}{\mathtt{9}}$$

$${\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{x}}{\mathtt{\,-\,}}{\mathtt{15}}$$

 Apr 17, 2015
 #2
avatar+980 
+8

I'm not sure if it's right, but I ended up with a quadratic by the end. Here goes:

$${\frac{{\mathtt{1}}}{{\mathtt{2}}}}{\mathtt{\,\small\textbf+\,}}{\frac{{\mathtt{2}}}{\left({\mathtt{5}}{\mathtt{\,\times\,}}{\mathtt{t}}\right)}}{\mathtt{\,-\,}}{\mathtt{1}} = {\frac{{\mathtt{1}}}{\left({\mathtt{5}}{\mathtt{\,\times\,}}{\mathtt{t}}\right)}}{\mathtt{\,\small\textbf+\,}}{\mathtt{t}}$$ Take the 1/5t off both sides.

$${\frac{{\mathtt{1}}}{{\mathtt{2}}}}{\mathtt{\,\small\textbf+\,}}{\frac{{\mathtt{1}}}{\left({\mathtt{5}}{\mathtt{\,\times\,}}{\mathtt{t}}\right)}}{\mathtt{\,-\,}}{\mathtt{1}} = {\mathtt{t}}$$ Multiply everything by 10t.

$${\frac{\left({\mathtt{10}}{\mathtt{\,\times\,}}{\mathtt{t}}\right)}{{\mathtt{2}}}}{\mathtt{\,\small\textbf+\,}}{\frac{\left({\mathtt{10}}{\mathtt{\,\times\,}}{\mathtt{t}}\right)}{\left({\mathtt{5}}{\mathtt{\,\times\,}}{\mathtt{t}}\right)}}{\mathtt{\,-\,}}{\mathtt{10}}{\mathtt{\,\times\,}}{\mathtt{t}} = {\mathtt{10}}{\mathtt{\,\times\,}}{{\mathtt{t}}}^{{\mathtt{2}}}$$ Simplify.

$${\mathtt{5}}{\mathtt{\,\times\,}}{\mathtt{t}}{\mathtt{\,\small\textbf+\,}}{\mathtt{2}}{\mathtt{\,-\,}}{\mathtt{10}}{\mathtt{\,\times\,}}{\mathtt{t}} = {\mathtt{10}}{\mathtt{\,\times\,}}{{\mathtt{t}}}^{{\mathtt{2}}}$$

$${\mathtt{10}}{\mathtt{\,\times\,}}{{\mathtt{t}}}^{{\mathtt{2}}}{\mathtt{\,-\,}}{\mathtt{5}}{\mathtt{\,\times\,}}{\mathtt{t}}{\mathtt{\,-\,}}{\mathtt{2}} = {\mathtt{0}}$$ Now using the quadratic formula,

$$t=\frac{-b+\sqrt{b^2-4ac}}{2a}$$ or $$t=\frac{-b-\sqrt{b^2-4ac}}{2a}$$

a=10, b=-5, c=-2

$$t=\frac{5+\sqrt{5^2-4\times{10}\times{-2}}}{2\times{10}}$$ or $$t=\frac{5+\sqrt{5^2-4\times{10}\times{-2}}}{2\times{10}}$$

$$t=\frac{5+\sqrt{25+80}}{20}$$ or $$t=\frac{5-\sqrt{25+80}}{20}$$

$$t=\frac{5+\sqrt{105}}{20}$$ or $$t=\frac{5-\sqrt{105}}{20}$$

which works out to $$\approx$$ 0.76235 or -0.26235.

P.S. I don't know how to say "plus minus" something.

 Apr 18, 2015
 #3
avatar+118667 
+11
Best Answer

Hi Zac,

 

Thanks for answering these questions :)

 

There is a couple of things here.

 

1) I think it should be       $$10t^2+5t-2=0\qquad (NOT -5t)$$

 

2) I am not sure what the asker INTENDED the question to be BUT this was the question.

 

1/2+2/5t-1=1/5t+t

 

Technically this should be interpreted as

$$\\\frac{1}{2}+\frac{2}{5}t-1=\frac{1}{5}t+t\\\\
\frac{1}{2}+\frac{2t}{5}-1=\frac{1t}{5}+t\qquad $The t is on the top$\\\\
\frac{-1}{2}+\frac{2t}{5}=\frac{6t}{5}\\\\
\frac{-1}{2}=\frac{4t}{5}\\\\
\frac{-1*5}{2*4}=t\\\\
t=\frac{-5}{8}\\\\$$

 

Also, I would like you to consider putting in some blank lines.  

Sometimes mine is spread out too much, I realize that, but I personally find it a bit hard to read when there are no spaces.  This may just be a peronal preference.  I am not sure :/

Melody Apr 18, 2015
 #4
avatar+4 
+5

-2(2x+3)+6x-9.                                                                                                                                                           (1      -4x+-6+6x-9

       2x+-15

_______________________________________________________________________________________________________

1/2+2/5t-1=1/5t+t                                                                                                                                                    (2

  -1/2+2/5t=1.2t

          -2\5t= -2/5t

    -2/1* -1/2=.8t*-2/1

               t=-1.6

 Apr 18, 2015

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