7c^2=91?
How do you solve this?

Question

7c^2=91?
How do you solve this?

anonymous · Answer

7c^2=91
  c^2=91/7
  c^2=13
     $$c=\pm \sqrt{13}$$

anonymous · Answer

THANK YOU! Now what about

n^2=83

anonymous · Answer

well when I had c^2=13 i took the plus or minus squareroot of 13.

what do you think the answer will be for n^2=83?

anonymous · Answer

n plus or minus the sq rt of 83??

anonymous · Answer

$$n \pm \sqrt{83}$$

anonymous · Answer

perfect :D

anonymous · Answer

what about 5x^2+12=87

phi · Answer

I'm sure you meant
$$ n = \pm \sqrt{83} $$

anonymous · Answer

ya i did but how do u solve the other one

phi · Answer

to solve, subtract 12 from both sides.
then divide by 5 (both sides)
then take the square root (of both sides)
what do you get?

phi · Answer

If this does not make sense, this and the following 2 videos might help http://www.khanacademy.org/video/simple-equations?topic=core-algebra it doesn't do square roots, but you have to walk before you can run.

anonymous · Answer

[x=\sqrt{15}\] is that right

phi · Answer

let's check
 5x^2+12=87, with x= sqrt(15)
5*sqrt(15)*sqrt(15)+12= 5*15+12= 75+12= 87 
yes, it works.

phi · Answer

all these types of problems follow the same pattern, so try another and see how it goes.