Current location - Training Enrollment Network - Mathematics courses - Solving two math problems in grade three (about practical problems and quadratic equations in one variable)
Solving two math problems in grade three (about practical problems and quadratic equations in one variable)
Let the length be x and the width be x-5.

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.