1 1 1 1 2 1 1 3 3 1 1 4 6 4 1 1 5 10 10 5 1
Pascal's triangle can be made as follows. On the first row, write only the number 1. Then, to get the numbers of following rows, add the number that can be seen above and to the left (if any) and the number above and to the right (if any) to find the new value. For example, the numbers 1 and 3 in the fourth row are added to make 4 in the fifth row.
Uses of Pascal triangle[change | edit source]
- (x + 1)2 = 1x2 + 2x + 12.
Notice the coefficients are the third row of Pascal's triangle: 1, 2, 1. In general, when a binomial is raised to a positive integer power we have:
- (x + y)n = a0xn + a1xn−1y + a2xn−2y2 + … + an−1xyn−1 + anyn,
where the coefficients ai in this expansion are precisely the numbers on row n + 1 of Pascal's triangle; in other words,
Pascal's rule[change | edit source]
for non-negative integers n and k where n ≥ k and with the initial condition
Complicated structures based on Pascal's triangle[change | edit source]
Pascal's triangle generalizes readily into higher dimensions. The three-dimensional version is called Pascal's pyramid or Pascal's tetrahedron. A higher-dimensional analogue is generically called a "Pascal's simplex"*. See also pyramid, tetrahedron, and simplex.
Properties of Pascal's Triangle[change | edit source]
The first and last number in each row is always 1.
The second number in each row is the row number. In a binomial expansion, this second number is equal to the power. (This makes the 'first' row, 1, actually the zero row).
The rows always read the same forward and backward.
The sum of the numbers in each row is double the sum of the numbers in the row before. The sum of each row is 2n.
- The zero row, 1, has a sum of 1.
- The first row, 1,1 has a sum of 2.
- The second row, 1,2,1 has a sum of 4.
- The third row, (1,3,3,1) has a sum of 8.
- The sum of the nth row is
Other websites[change | edit source]
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