Here's the question you clicked on:
Ledah
Two regular decagons have areas of 30 mm² and x² + 7x mm². What values of x make the decagons congruent?
Since the areas are equal, equate the expressions for both areas: \[30 = x^2 + 7x\] Now, bring every term to the same side, and lo! you have a quadratic. solve it, find 'x' and enjoy!
Two polygons are congruent if they are exactly the same. What can you say about the area of two congruent polygons?
They should also be the same
So, all you have to do is equate their areas and get a quadratic equation as obtained by @apoorvk and solve it.
I got 5 and -6 as an answer.. I'm not sure if its right I'm still checking my work
Umm, sorry that isn't correct - did you split the middle term and factorize it?
\(x=5\) does not satisfy the equation. What you have is \(x^{2}+7x-30 = 0\) Can you factorise the left hand side?