Solve the equation by completing the square. If nessecary, round to the nearest hundreth x^2-18x=19

Question

anonymous · Answer

x^2-18x-19=0

anonymous · Answer

(x-9)^2-100

anonymous · Answer

$$(x-9)^{2}-100$$

mertsj · Answer

half of 18 is 9 and 9^2 is 81 so add 81 to both sides:
$$x^2-18x+81=19+81$$

mertsj · Answer

Now factor the left side:
$$(x-9)^2=100$$

mertsj · Answer

Now take the square root of both si:
$$x-9=\pm10$$

mertsj · Answer

Now add 9 to both sides:
$$x=10+9=19, x=-10+9=-1$$

anonymous · Answer

only 1;19 -1;19 3;6 and -3;1

anonymous · Answer

wait so its-1 19??

mertsj · Answer

The answers are
 x=19
x=-1

anonymous · Answer

thank you can you help me with one more?

anonymous · Answer

Which model is most appropriate for the data shown in the graph below?

mertsj · Answer

Looks like a parabola with vertex (-1,0).  What do you think?

anonymous · Answer

i think its an exponential

mertsj · Answer

What are your choices?

anonymous · Answer

quadratic linear exponential and line

mertsj · Answer

If it is a parabola, its equation should be y = a(x-h)^2+k
We know (h,k) is (-1,0) and we see that (1,1) is on the graph. So let's calculate the value of a and see if the other given points fit.  If not, then it's an exponential.

mertsj · Answer

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