Meaning: x*(x-5)*6=396.

x ^ 2-5x-66 = 0。

(x- 1 1)(x+6)=0

Because x>0

So x- 1 1=0.

That is, x= 1 1, so the length is 1 1 cm and the width is 6 cm.

The square is represented by 2.

Have equal real roots.

Then the discriminant △ = (k+2) 2-16 (k-1) = 0.

That is, k 2- 12k+20 = 0.

That is, (k-2)(k- 10)=0.

k 1=2，k2= 10

When k=2, the equation is 4x 2-4x+ 1 = 0, and the solution is x 1=x2= 1/2.

When k= 10, the equation is 4x 2- 12x+9 = 0, and the solution is x 1=x2=3/2.