If you square the equation v=v0 + at, you'll have an expression for v2. Equate the two expressions for v2, and show that the resulting equation reduces to the equation x= x0+v0t + 1/2at2.
2 answers
What is the second of the two expressions for v^2 that you are referng to?
To drwls v2= vo2+ 2a(x-x0)