Mathematics Grade 12 15 min

Pascal's triangle

Pascal's triangle

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Introduction & Learning Objectives

Learning Objectives Construct Pascal's triangle to any specified row. Identify the relationship between the entries in Pascal's triangle and binomial coefficients, denoted as C(n, k) or \(\binom{n}{k}\). Use Pascal's triangle to quickly find the coefficients for the expansion of a binomial of the form (a + b)^n. Expand binomials with coefficients and multiple variables, such as (2x - 3y)^5, using Pascal's triangle. Determine a specific term or coefficient within a binomial expansion without performing the full expansion. Apply the Binomial Theorem as a formal generalization of the patterns observed in Pascal's triangle. Recognize and describe key properties of Pascal's triangle, including its symmetry and the sum of its rows. How could you fin...
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Key Concepts & Vocabulary

TermDefinitionExample Pascal's TriangleA triangular array of numbers where each number is the sum of the two numbers directly above it. The edges of the triangle are all 1s.Row 4 is 1, 4, 6, 4, 1. The '6' is the sum of the '3' and '3' from Row 3 above it. Binomial ExpansionThe process of multiplying a binomial (a + b) by itself 'n' times. The result is a polynomial with n+1 terms.The expansion of (a + b)² is a² + 2ab + b². Binomial CoefficientThe numerical coefficients of the terms in a binomial expansion. These coefficients correspond to the entries in Pascal's triangle.In the expansion (a + b)³, which is 1a³ + 3a²b + 3ab² + 1b³, the binomial coefficients are 1, 3, 3, 1. Combination (nCr)The number of ways to choose 'r' elements...
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Core Formulas

Pascal's Triangle Construction Rule Entry(n, k) = Entry(n-1, k-1) + Entry(n-1, k) Any entry in the triangle is the sum of the two entries directly above it in the previous row. The edges (where k=0 or k=n) are always 1. Binomial Coefficient Formula \(\binom{n}{k} = C(n, k) = \frac{n!}{k!(n-k)!}\) This formula directly calculates the entry in the nth row and kth position of Pascal's triangle. It represents the number of ways to choose k items from a set of n. The Binomial Theorem \((a+b)^n = \sum_{k=0}^{n} \binom{n}{k} a^{n-k} b^k\) This is the formal rule for binomial expansion. It states that for any term in the expansion, the coefficient is \(\binom{n}{k}\), the power of 'a' is n-k, and the power of 'b' is k.

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Sample Practice Questions

Challenging
What is the constant term (the term independent of x) in the expansion of \((x^2 + \frac{2}{x})^6\)?
A.240
B.160
C.15
D.60
Challenging
What is the sum of all the coefficients in the full expansion of (2x - 3y)⁴?
A.625
B.1
C.-1
D.0
Challenging
Find the coefficient of the x⁶y² term in the expansion of (2x³ - y)⁴.
A.96
B.24
C.-24
D.6

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