Simplified to a2+b2=c2,

In other words, the square of the hypotenuse of a right triangle is equal to the sum of the squares of two right angles.

(2) As shown:

From the figure, we can get (a+b) 2 = C2+4× 12ab.

So A2+B2 = C2.

(3)c2=a2+b2=(a+b)2-2ab=49-24=25，

∴c=5.