Geometry equation: x squared + 3x = 8x + 6

Hello, alee!


\(\displaystyle \L \;x^2\,+\,3x\,=\,8x\,+6\)


Let get this in the form \(\displaystyle \,ax^2\,+\,bx\,+c\,=0\,\) to solve the quadratic:


\(\displaystyle \L \;x^2\,-\,5x\,-\,6\,=\,0\)


Where are you stuck? What have you tried?
 
stuck on what to do with the xsquared. I know x squared -5x = 6
 
alee said:
stuck on what to do with the xsquared. I know x squared -5x = 6

Well why didn't you say so? :wink:


Let use the simple 'ole factoring method for this. What 2 number multiply to give you \(\displaystyle - 6\) and add up to \(\displaystyle - 5\) ? Those are \(\displaystyle - 6\,&\,1\).


So now we have:\(\displaystyle \L \;(x\,+\,1)\,\,(x\,-\,6)\,=\,0\)

Which is saying solve these two equations:


\(\displaystyle \L \;x\,+\,1\,=\,0\)


\(\displaystyle \L \;x\,-\,6\,=\,0\)


Those will be your two roots of \(\displaystyle x\).
 
or, xsquared - 5x - 6 = 0
x squared - 5x - 6 = (x+6)(x-1) = 0
therefore x = -6 and 1
 
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