`1) x^2 + 10x + 26 + y^2 + 2y`
` = (x^2 +10x + 25) + (y^2 + 2y + 1)`
` = (x + 5)^2 + (y+1)^2`
`2) z^2 - 6z + 13 + t^2 + 4t`
` = (z^2 - 6z + 9) + (t^2 + 4t+4)`
` = (z - 3)^2 + (t+2)^2`
`3) x^2 - 2xy + 2y^2 + 2y + 1`
` = (x^2 - 2xy + y^2) + (y^2 + 2y + 1)`
` = (x-y)^2 + (y+1)^2`
`4) 4x^2 + 2z^2 - 4xz - 2z + 1`
` = (4x^2 - 4xz + z^2) + (z^2 - 2z + 1)`
` = (2x - z)^2 + (z - 1)^2`
`5) 4x^2 - 12x - y^2 + 2y + 8`
`= (4x^2 - 12x + 9) - (y^2 - 2y + 1)`
` = (2x - 3)^2 - (y-1)^2`
