(1)2x- 1= root number 3 or-root number 3.

X= (root number 3+ 1)/2 or (-root number 3+ 1)/2.

(2)x^2=25

X=5 or -5

(3)(3x-6)(x-2)=x(x-2)

(2x-6)(x-2)=0

2x-6=0 or x-2=0.

X=3 or 2

⑷2x^2- 1 1x+2=0

delta=(- 1 1)^2-4*2*2= 105

X=( 1 1+ radical number 105)/4 or (1-radical number 105)/4.

(according to formula)

2.( 1)delta=k^2-4* 1*(-6)

=k^2+24>； 0

So there are two unequal real roots.

(2) According to Vieta's theorem, two roots X 1+X2 =-k/ 1 =-k, X 1 * X2 =-6/ 1 =-6.

Because x 1=- 1, x2=-6/- 1=6.

So x 1+x2=- 1+6=5.

That is -k=5.

So k=-5

To sum up, k=-5 and the other one is 6.

3. Let the price reduction range be x each time.

144( 1-x)^2= 100

( 1-x)^2= 100/ 144

( 1-x)=5/6

x= 1/6

That is, every price reduction 1/6, that is 16.7%.