Robert Recorde, The designer of the equals sign, introduced plus and minus to Britain in 1557 in The Whetstone of Witte:[14] "There be other 2 signes in often use of which the first is made thus + and betokeneth more: the other is thus made − and betokeneth lesse." Bij https://www.openlearning.com/u/emeryoneill-sx1bu1/about/