who started to use x,y,z  in math problems?instead of a,b,c ?
214048
some weirdo dude,\nduh!
463723
You have a couple of typos, I think.  As for the "proof", dividing by x - y is dividing by zero.  That is a no-no.  (In other words, a * 0 = b * 0 does not imply a = b.)
494540
1. y-axis\n\n2. 2nd quadrant\n\n3. 2nd or 3rd quadrants\n\n4. 2x + 3y = 6 => y = 2 - (2/3)x\n\n5. x - 2y = 8 => y = (1/2)x - 4\n\n6. x - 3y = 4 => x = 4 + 3y\n   Only (a) is a solution\n\n7. y - 2x = -1 => y = -1 + 2x\n   (b), (c) are solutions
428809
I think it was Rene Descartes who said "I think so therefore I am."  Whatta guy, not only a philosopher, but he developed the Cartesian coordinate system--y'know, used for graphing equations and functions using the x- and y-axes.
531255
it is natural to write the equation of st.line as y=ax+b (now common form is y=mx+c; this has its own story!)\n\nso if x=0, y=b
236422
Am I doing your homework for you?\n1. A and B\n2. B and C\n3. C\n4. A\n5. B and D\n6. A\n7. B
2847
You can.  Use the mapping (x, y, z) -> x.  Of course, that is a many-to-one mapping, and kind of useless.
545891
It might be a little to high of a level but thesymbol for integers Z (in set theoy) comes from the german word for number.  Also, in cardinality of sets uses some hebrew letters.  Algebra is an Arabic word.  Our number system is called the Hindu-Arabic.  \n\nWikipedia has some good stuff on math history....\n\nOf course, lots of things are named for the developer.  Cartesian coordinate for Descarte.  Gaussian, or normal, distibution: the so-called bell curve.  Pythagoras...Fibonacci numbers...
485557
1. x-y=9---------------------(1)\nx+y=7-----------------------(2)\nadding\n2x=16\ndividing by 2\nx=8\nsub in 1,\ny=-1\n\n2. 5x-4y=12--------(1)\n3x-4y=4-------------(2)\n(1)-(2)\n2x=8\ndividing by 2\nx=4\nsub in 1 \ny=2\n\n3. 3x+3y=6-----------(1)\n2x-y=1-----------------(2)*3\n6x-3y=3---------------(3)\n(1)+(3)\n9x=9\ndividing by 9\nx=1\nsub in (1)\ny=1\n\n4. 3x-5y=13-----------(1)*3\n4x+3y=17--------------(2)*5\n9x-15y=39\n20x+15y=85\nadding\n29x=124\ndividing by 29\nx=124/29\nsub and find y\n\n5. x-y=1---------(1)\n3x-y=10---------(2)\n(2)-(1)\n2x=9\ndividing by 2\nx=9/2\nsuby=7/2\n\n6. 4x=2y-7\nthe other equation is missing\nx=(2y-7)/4\n\n7. y=-2x-----------(1)\n5x+3y=-3---------(2)\nsub y=-2x in (2)\n5x+3(-2x)=-3\n5x-6x=-3\n-x=-3\nx=3\nsub\ny=-6\n\n8. x+y=6---------(1)\n-2x+y=-3---------(2)\nsubtracting\n3x=9\ndividing by 3\nx=3\nsub\ny=3\n\n9. 2x+y=45-----------(1)\n3x-y=5-----------------(2)\nadding\n5x=50\ndividing by 5\nx=10\nsub\ny=25
236314
Now keep in mind I am a recent college graduate...but I remember when I took Algebra 2, I struggled some...ended up with like a B (I think..hard to remember those details).  I did much better with Geometry though-so thats cool. I enjoy math though-isn't that ironic? I did very well in college though.
52549
You are solving for k so it you need to rewrite the problem to look like this k=z/(xy) where x=3, y=8, z=6 substitute the letters for numbers so k=6/(3*8) k=6/24 or k=1/4 to check just solve for any other letter such as z by using what you know of k and you should come out with z=6
154820
No offense to the others.. but they are going about this all wrong.\n\n2*(y^2)*(x+y) when x=7 and y=8\n     First you do (y^2).. so (8^2) which is 64\n     Then you add (x+y).. so (7+8) which is 15\n     Now rewrite the equation.. so 2*64*15 which is 1920\n\n2*(y^2)*(x+y) when x=5 and y=6\n     First you do (y^2).. so (6^2) is 36\n     Then you add (x+y).. so (5+6) is 11\n     Now rewrite the equation.. so 2*36*11 which is 792
458162
1)1,8,27,64,125\n  x^3 = 1^3, 2^3, 3^3, 4^3, 5^3\n\n2)9, 13, 15, 19, 21, 25\n a(n)+ n-2 = {a(n-1) +a(n+1)}/2\n\n3)00001, 00011, 00101, 00111, 01001\n  1,3,5,7,9 in binary\n\n4)17,23,5,18,20,25,21,9,15,16\nok, your teacher is an ass for this one..  heres the breakdown\nq is the 17th letter, w is the 23 letter, e, r, t, y, u, i, o, p\nthe top row of a standard U.S. keyboard. i think i earned 10 points for that one alone\n\n\n5)\nFOUR\nF I V E\nN I N E\n\nR=0\nF=2\nI=3\nN=5\nE=6\nU=7\nV=8\nO=9\n\n2970 + 2386 = 5356\nDONE.  Hope this works for you
534868
Brackets, Orders, Division, Multiplication, Addition, Subtraction.\nIn some countries its BEDMAS, where E is exponents.
414502
Let y = ax² + bx + c\n\nWhen x = 1; y = a + b + c = 12 ............ (1)\nWhen x = 2; y = 4a + 2b + c = 22 ........ (2)\nWhen x = 3; y = 9a + 3b + c = 30 ........ (3)\n\nOn solving you get a = -1 b = 13 c = 0\n\nie y = 13x - x²\n\nAgree with Antoine above
267165
Blaise Pascal? He invented the calculator. Maybe Isaac Newton, the inventor of calculus, or Charles Babbage, the inventor of the computer. Perhaps John Napier, who discovered how to add, subtract, multiply, divide, and even extract square roots simply by moving pieces on a chessboard? Tell you what, pick René Descartes, he's the inventor of coordinate geometry. These are all excellent choices!
164889
The origins of algebra can be traced to the ancient Babylonians, who developed an advanced arithmetical system with which they were able to do calculations in an algebraic fashion. With the use of this system they were able to apply formulae and calculate solutions for unknown values for a class of problems typically solved today by using linear equations, quadratic equations, and indeterminate linear equations. By contrast, most Egyptians of this era, and most Indian, Greek and Chinese mathematicians in the first millennium BC usually solved such equations by geometric methods, such as those described in the Moscow and Rhind Mathematical Papyri, Sulba Sutras, Euclid's Elements, and The Nine Chapters on the Mathematical Art. This geometric work of the Greeks, typified in the Elements provided the framework for generalizing formulae beyond the solution of particular problems into more general systems of stating and solving equations.\n\nIndian mathematicians proceeded to write treatises on algebraic means of solving equations from the end of the first millennium BC, followed by Hellenistic mathematicians from the early first millennium AD. Important algebraic works from this general era include the Bakhshali Manuscript, the works of Hero of Alexandria, the Arithmetica of Diophantus, the Aryabhatiya of Aryabhata, and the Brahma Sputa Siddhanta of Brahmagupta.\n\nThe word "algebra" is named after the Arabic word "al-jabr" from the title of the book al-Kitāb al-muḫtaṣar fī ḥisāb al-ğabr wa-l-muqābala, meaning The book of Summary Concerning Calculating by Transposition and Reduction, a book written by Persian mathematician Muḥammad ibn Mūsā al-Ḵwārizmī in 820. The word al-jabr means "reunion". Al-Khwarizmi is often considered the "father of algebra" (though that title is also given to Diophantus), as much of his works on reduction are still in use today. Another Persian mathematician Omar Khayyam developed algebraic geometry and found the general geometric solution of the cubic equation. Indian mathematician Bhaskara and Chinese mathematician Zhu Shijie solved cubic, quartic (biquadratic) and higher-order polynomial equations.\n\nAnother key event in the further development of algebra was the general algebraic solution of the cubic and quartic equations, developed in the mid-16th century. The idea of a determinant was developed by Japanese mathematician Kowa Seki in the 17th century, followed by Gottfried Leibniz ten years later, for the purpose of solving systems of simultaneous linear equations using matrices. Gabriel Cramer also did some work on matrices and determinants in the 18th century. Abstract algebra was developed in the 19th century, initially focusing on what is now called Galois theory, and on constructibility issues.\n\nThe stages of the development of symbolic algebra are roughly as follows:\nRhetorical algebra, which was developed by the Babylonians and remained dominant up to the 16th century;\nGeometric constructive algebra, which was emphasised by the Vedic Indian and classical Greek mathematicians;\nSyncopated algebra, as developed by Diophantus and in the Bakhshali Manuscript; and\nSymbolic algebra, which sees its culmination in the work of Leibniz.\n \nCover of the 1621 edition of Diophantus' Arithmetica, translated into Latin by Claude Gaspard Bachet de Méziriac.\n\nA timeline of key algebraic developments are as follows:\nCirca 1800 BC: The Old Babylonian Strassburg tablet seeks the solution of a quadratic elliptic equation.\nCirca 1600 BC: The Plimpton 322 tablet gives a table of Pythagorean triples in Babylonian Cuneiform script.\nCirca 800 BC: Indian mathematician Baudhayana, in his Baudhayana Sulba Sutra, discovers Pythagorean triples algebraically, finds geometric solutions of linear equations and quadratic equations of the forms ax2 = c and ax2 + bx = c, and finds two sets of positive integral solutions to a set of simultaneous Diopha