SOLUTION: i need help solving the equation graphically and then checking the results algebraially {{{3x^2+12x=-9}}}

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Question 775456: i need help solving the equation graphically and then checking the results algebraially 3x%5E2%2B12x=-9
Answer by sofiyac(983) About Me  (Show Source):
You can put this solution on YOUR website!
3x%5E2%2B12x=-9
3x%5E2%2B12x%2B9=0 instead of 0 put y there
3x%5E2%2B12x%2B9=y
now make a table of x and y, plug in any value of x you want and solve for y, do this about 5 times so you have 5 points. Example if x=0 then y=9 so first point could be (0,9) and so on. Then plot the points and connect the dots
+graph%28+300%2C+200%2C+-5%2C+1%2C+-10%2C+10%2C+3x%5E2%2B12x%2B9%29+
looks like solutions fall at x=-3 and x=-1 so now plug those values in one at a time to check the solutions
3x%5E2%2B12x=-9
if x=-3 then
27-36=-9
-9=-9 left=right
if x=-1 then
3-12=-9
-9=-9 left=right