Mathematics
Grade 11
15 min
Squares up to 10 x 10
Squares up to 10 x 10
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1
Introduction & Learning Objectives
Learning Objectives
Represent any integer square, such as 8², as a perfect square trinomial using binomial expansion, like (10-2)².
Apply the difference of squares formula to mentally calculate the difference between two squares, such as 9² - 7².
Model the sequence of squares (1, 4, 9, ..., 100) with the polynomial function f(n) = n² and analyze its properties.
Prove that the second differences of the sequence of squares are constant, confirming its quadratic nature.
Calculate the sum of squares from 1² to 10² using the formula for the sum of the first n squares.
Generalize patterns observed in squares up to 10 x 10 to prove properties of integers using polynomial identities.
You've known that 9 x 9 = 81 since elementary school, but can you prove it using the polynomial...
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Key Concepts & Vocabulary
TermDefinitionExample
Perfect Square TrinomialA trinomial that results from squaring a binomial. It follows the pattern a² + 2ab + b² or a² - 2ab + b².The square 7² can be expressed as (5+2)². Expanding this gives the perfect square trinomial 5² + 2(5)(2) + 2² = 25 + 20 + 4 = 49.
Difference of SquaresA binomial in the form a² - b², which can be factored into the product of a sum and a difference, (a+b)(a-b).To find 10² - 8², we can factor it as (10+8)(10-8), which simplifies to (18)(2) = 36. This matches the direct calculation 100 - 64 = 36.
Quadratic FunctionA polynomial function of degree 2, with the general form f(x) = ax² + bx + c. The sequence of squares is generated by the simplest quadratic function.The function f(n) = n² generates the sequence of squares. For n=1, 2, 3, ..., 10, t...
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Core Formulas
Perfect Square Trinomial (Addition)
(a + b)² = a² + 2ab + b²
Use this formula to expand the square of a binomial sum. This is useful for mental math and for deriving properties of numbers.
Perfect Square Trinomial (Subtraction)
(a - b)² = a² - 2ab + b²
Use this formula to expand the square of a binomial difference. Note that the final term, b², is positive.
Difference of Squares
a² - b² = (a - b)(a + b)
Use this formula to quickly factor expressions or to calculate the difference between two squared numbers.
Sum of the First n Squares
Σ_{i=1}^{n} i² = \frac{n(n+1)(2n+1)}{6}
A powerful formula to find the sum of the first 'n' consecutive perfect squares without adding them individually. This is a key formula in the study of sequences and series.
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Challenging
The sum of the first n squares is 385. By solving the polynomial equation n(n+1)(2n+1)/6 = 385, what is the value of n?
A.8
B.9
C.10
D.11
Challenging
Let f(n) = n². The average rate of change from n=a to n=b is (f(b)-f(a))/(b-a). What is the average rate of change for the function from n=5 to n=8?
A.3
B.13
C.39
D.6.5
Challenging
The difference between the squares of two consecutive odd integers is 80. If the integers are represented by (2n+1) and (2n+3), what is the value of the larger integer?
A.19
B.21
C.23
D.25
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