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csawic
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even + even = even * even =
odd + odd = odd * odd =
even + odd = even * odd =
 even + even = even even * even = even
 odd + odd = even odd * odd = odd
 even + odd = odd even * odd = even

prime numbers through 30
2, 3, 5, 7, 11, 13, 17, 19, 23, 29

divisibility
 by 3 if sum of digits = 3
 by 4 if last two digits of the number are divisible by 4
 by 5 if it ends in 0 or 5
 by 6 if its divisible by both 2 and 3
 by 8 if the last 3 digits form a number divisible by 8
 by 9 if the sum of the gidits is divisible by 9

Rules of Exponents
a^{2} = a * a
a^{2} * a^{3} = a^{2+3} = a^{5
}(a^{2})^{3} = a^{6
}a^{2}/a^{3} = a^{23} = a^{1} = 1/a
15^{12}  15^{11} = 15^{11}(151) = 15^{11}(14)

Rules of Square Roots
 can mult and divide square roots by each other
 can only add/subtract intigers in fromt of root if its the SAME root
 on GRE square root only includes the positive answer, but can square neg numbers to equal positive number

square root of 2 =
square root of 3 =
square root of 2 = 1.4
square root of 3 = 1.7

Quadratic Equations
x^{2} y^{2} = (x + y)(x  y)
(x + y)^{2} = x^{2} + 2xy + y^{2}
(x  y)^{2} = x^{2}  2xy + y^{2}

