Question 858686
x^2+p+x=3(x+1) 

x^2+p+x=3x+3

x^2-2x+(p-3)=0

For roots to be equal

the discriminant b^2-4ac =0 in the equation ax^2+bx+c=0

here a= 1, b= -2 c= (p-3)

-2^2 - 4*1*(p-3)=0

4-4p+12=0

4p=16
p=4