anonymous
  • anonymous
how do i graph g(x)=-2(x-1)^2+7 given this, i know that the vertex is (1,7) how do i find the x intercepts?
Mathematics
  • Stacey Warren - Expert brainly.com
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SOLVED
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katieb
  • katieb
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anonymous
  • anonymous
set g(x)=0
anonymous
  • anonymous
then i use the quadratic formula?
anonymous
  • anonymous
yes, but you don't have to go that far, you can just subtract 7 from each side, divide by -2 on each side, and take square root of each side

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More answers

anonymous
  • anonymous
remember when you square root on each side you have a positive and negative
anonymous
  • anonymous
do i have to expand the (x-1)^2?
anonymous
  • anonymous
so it would look like -2x^2-2x+8
anonymous
  • anonymous
you don't have to if you do it the way i suggested. it's up to you if you're more comfortable using the quadratic formula
anonymous
  • anonymous
if you expanded you would have: -2(x^2-2x+1)+7= -2x^2+4x-2+7= -2x^2+4x+5
anonymous
  • anonymous
so from where u left off i could use the quadratic formula
anonymous
  • anonymous
yes
anonymous
  • anonymous
im curious about the method that u earlier mentioned, would i get the same results as to using quadratic formula?
anonymous
  • anonymous
yes
anonymous
  • anonymous
you solve like a regular algebra problem
anonymous
  • anonymous
and i can use that for all equations!? :O
anonymous
  • anonymous
does "completing the square" sound familiar?
anonymous
  • anonymous
yeah my teacher told me thats how we find the vertex
anonymous
  • anonymous
but we already found the vertex since its given in the equation here
anonymous
  • anonymous
yes, there are a couple ways to find vertex. u can also easily find vertex when problem is in form ax^2+bx+c, the vertex is at (-b/(2a),f(-b/(2a)))
anonymous
  • anonymous
im getting something really weird when i punch it into the quadratic formula
anonymous
  • anonymous
you will get irrational zeros
anonymous
  • anonymous
the heck, how do i graph it then? @_@
anonymous
  • anonymous
\[x=\frac{2 \pm \sqrt{14}}{2}\]
anonymous
  • anonymous
use a calculator to get decimal approximation
anonymous
  • anonymous
x=-0.87 or x=2.87
anonymous
  • anonymous
oh yeah! and for this the answer you got above did u factor out the 2 or something?
anonymous
  • anonymous
yes, i factored
anonymous
  • anonymous
how did u factor it when there's a +5?
anonymous
  • anonymous
-2x^2+4x+5 -2(x^2+2x) + 5?
anonymous
  • anonymous
f(x)=-2x^2+4x+5 \[x=\frac{-4 \pm \sqrt{16-4(-2)(5)}}{2(-2)}\] \[x=\frac{-4 \pm \sqrt{56}}{-4}=\frac{-4 \pm \sqrt{14*4}}{-4}=\frac{-4 \pm 2\sqrt{14}}{-4}=\frac{-2 \pm \sqrt{14}}{-2}=\frac{2 \pm \sqrt{14}}{2}\]
anonymous
  • anonymous
thank you very much appreciated your assistance, again
anonymous
  • anonymous
you're welcome

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