TweenPosition is not a valid member of Frame?

I'm trying to make a simple tween GUI, but for some reason it's not working because of the error in the title above. Here's my script:

local gui = script.Parent.Parent.Parent
local frame = gui.mainframe
local frame2 = gui.teamframe

frame.play.MouseButton1Click:Connect(function()
	frame:TweenPostition(UDim2.new(-1, 0,0, 0))
	frame2:TweenPosition(UDim2.new(0, 0,0, 0))
end)