To add the vectors (x₁,y₁) and (x₂,y₂), we add the corresponding components from each vector: (x₁+x₂,y₁+y₂). Here's a concrete example: the sum of (2,4) and (1,5) is (2+1,4+5), which is (3,9). There's also a nice graphical way to add vectors, and the two ways will always result in the same vector.​​

All art is political in the sense that all art takes place in the public arena and engages with an already existing ideology. Chinese artist, Ai Weiwei, offers an important contemporary example. The news that Chinese artist Ai Weiwei has been detained by authorities has prompted significant concern. Ai Weiwei has ben arrested by the Chinese authorities.

In this art history video discussion Beth Harris and Steven Zucker look at Albrecht Durer's "Self-Portrait, 1500." (Alte Pinakothek, Munich).

This art history video examines the "Alexander Mosaic" c. 100 B.C.E., tessera mosaic from the House of the Faun, Pompeii. This Roman floor mosaic may be based on a lost Hellenistic painting by Philoxenos of Eretria, The Battle of Issus, c. 315 B.C.E.). Museo Archeologico Nazionale, Naples.

This site teaches Arithmetic with Polynomials and Rational Expressions to High Schoolers through a series of 4333 questions and interactive activities aligned to 26 Common Core mathematics skills.

This site teaches High Schoolers how to create equations through a series of 298 questions and interactive activities aligned to 5 Common Core mathematics skills.

This site teaches Reasoning with Equations and Inequalities to High Schoolers through a series of 5909 questions and interactive activities aligned to 36 Common Core mathematics skills.

This site teaches Structure in Algebraic Expressions to High Schoolers through a series of 3482 questions and interactive activities aligned to 26 Common Core mathematics skills.

This art history video discussion examines Washington Allston's "Elijah in the Desert", 1818, oil on canvas, 125.09 x 184.78 cm / 49 1/4 x 72 3/4 inches (Museum of Fine Arts, Boston).

This art history video discussion examines Sir Lawrence Alma-Tadema's "A Reading from Homer", 1885, oil on canvas, (Philadelphia Museum of Art).

In this art history video discussion Beth Harris and Steven Zucker examine Albrecht Altdorfer's "The Battle of Issus," 1529, oil on panel. Alte Pinokothek, Munich.

In this art history video discussion Dr. Beth Harris and Dr. Steven Zucker consider Ambrogio Lorenzetti's series of frescos "Allegory of Good Government", "Effects of Good Government in the City and the Country", and "Allegory and Effects of Bad Government in the City and the Country" Siena c. 1337-40. Sala della Pace (Hall of Peace) also known as the Sala dei Nove (the Hall of the Nine), Palazzo Pubblico, Siena.

This art history video discussion examines a project between Khan Academy and Rome Reborn - with Dr. Bernard Frischer.

This art history video discussion examines Andrea Mantegna's "Camera degli Sposi" (Frescos in the ducal palace, Mantua), 1465-74.

This art history video discussion examines Andrea Pisano, Reliefs for the Campanile in Florence, c. 1336.

This art history video discussion examines Antoine or Louis Le Nain's "Peasant Family in an Interior", 2nd quarter of the 17th century, oil on canvas (Musee du Louvre, Paris).

This art history video discussion examines Apollonius' "Boxer at Rest", c. 100 B.C.E., bronze, Palazzo Massimo, Museo Nazionale Romano, Rome.

This art history video discussion examines the Arch of Constantine, 315 C.E., Rome.

This art history video discussion examines the Arch of Titus, originally Pentelic marble, early 19h-century restoration is in travertine, c. 81 C.E. (Via Sacra, Rome).

This arithmetic lesson demonstrates more long division problems with remainders.[Arithmetic playlist: Lesson 26 of 38]