http://mathdl.maa.org/mathDL/46/?pa=content&sa=viewDocument&nodeId=2591&bodyId=3599

The invention of the = sign

Robert Recorde 1550

The invention of the = sign

Robert Recorde 1550

The first equations ever written in English

14x + 15 = 71,

solution is 4.

Recorde explains subtraction using a poem

http://mathdl.maa.org/mathDL/46/?pa=content&sa=viewDocument&nodeId=2591&bodyId=3599

The first equations ever written in English

Robert Recorde in The Whetstone of Witte 1557.

The equation in modern terms, by

14x + 15 = 71,

whose solution is 4.

Recorde introduces for the first time, the "equal" sign.  He explains that he picked two parallel lines to represent this concept "because no two things can be more equal."

n English: The first equation ever written, by Robert Recorde in his treatise The Whetstone of Witte, in 1557. The equation is represented, in modern terms, by 14x + 15 = 71, and its solution is 4.

The Whetstone of Witte is the shortened title of Robert Recorde's mathematics book published in 1557. The full title being, The Whetstone of Witte, whiche is the seconde parte of Arithmeteke: containing the extraction of rootes; the cossike practise, with the rule of equation; and the workes of Surde Nombers, the book covers topics including whole numbers, the extraction of roots and irrational numbers.The work is notable for containing the first recorded use of the equals sign and also the first book in English to use the plus and minus signs. However, exponentiation was represented by a cumbersome form of mathematical notation in which indices and surds were represented by their prime factors (see Prime factor exponent notation).

The Whetstone of Witte is the shortened title of Robert Recorde's mathematics book published in 1557. The full title being, The Whetstone of Witte, whiche is the seconde parte of Arithmeteke: containing the extraction of rootes; the cossike practise, with the rule of equation; and the workes of Surde Nombers, the book covers topics including whole numbers, the extraction of roots and irrational numbers.The work is notable for containing the first recorded use of the equals sign and also the first book in English to use the plus and minus signs. However, exponentiation was represented by a cumbersome form of mathematical notation in which indices and surds were represented by their prime factors (see Prime factor exponent notation).

http://nsm1.nsm.iup.edu/gsstoudt/history/images/witte.html

The invention of the = sign

Robert Recorde 1550

On this page (Sig. S, f. i v & f. 2 r), Recorde explains the notation for a unknown and its various powers.  Note that the owner of this particular copy wrote notes to help him understand the various names and abbreviations for the powers. 

Recorde explains subtraction of polynomials by use of a poem (Sig. X, f. ii r).

On this page (Sig. Ff, f. i r), we see Recorde introducing, for the first time, the "equal" sign.  He explains that he picked two parallel lines to represent this concept "because no two things can be more equal." He then gives various examples of the use of the equal sign in algebraic equations.

On these pages (Sig. Ii, f. iv r & v and Sig. Kk, f. i r) is Recorde's attempt to design a real problem whose solution requires a quadratic equation.  This problem is entitled a "question of jorneying" and requires knowledge of the formula for the sum of an arithmetic progression.

The Whetstone of Witte by Robert Recorde (1557)

Recorde's algebra text where two equal parallel line segments as the symbol for equality was used for the first time: "bicause noe 2 thynges can be moare equalle".

http://nsm1.nsm.iup.edu/gsstoudt/history/images/witte.html

http://www.laputanlogic.com/articles/2004/04/13-0002.html

Robert Recorde