McGraw Hill Glencoe Algebra 2, 2012
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McGraw Hill Glencoe Algebra 2, 2012 View details
6. The Binomial Theorem
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Exercise 36 Page 702

You can find the coefficients of the required terms by using the Binomial Theorem. Alternatively, use the fact that the Pascal's triangle will be symmetric.

False, see solution.

Practice makes perfect

By using the Binomial Theorem we can write the given expression using sigma notation. (x+y)^(20) = ∑_(k=0)^(20) 20!/k!(20-k)!x^(20-k)y^kThe eighth term of the expression is found when k=7 and the twelfth term is the one when k=11. Let's substitute k=7 to find the eighth coefficient.

20!/k!(20-k)!
20!/7!(20- 7)!
â–¼
Simplify
20!/7!* 13!

Write as a product

20* 19* 18* 17 * 16 * 15 * 14 * 13!/7!* 13!
20* 19* 18* 17 * 16 * 15 * 14 * 13!/7!* 13!

Write as a product

20* 19* 18* 17 * 16 * 15 * 14/7* 6* 5 * 4* 3 * 2
20* 19* 18* 17 * 16 * 15 * 14/6* 4* 15 * 14
20* 19* 18* 17 * 16/6* 4
1 860 480/24
77 520

Similarly, let's substitute k=11 to find the twelfth coefficient.

20!/k!(20-k)!
20!/11!(20- 11)!
â–¼
Simplify
20!/11!* 9!

Write as a product

20* 19* 18* 17 * 16 * 15 * 14 * 13* 12 * 11!/11!* 9!
20* 19* 18* 17 * 16 * 15 * 14 * 13* 12 * 11!/11!* 9!

Write as a product

20* 19* 18* 17 * 16 * 15 * 14 * 13* 12/9* 8* 7 * 6 * 5* 4* 3 * 2
20* 19* 18* 17 * 16 * 15 * 14 * 13* 12/9* 7* 6* 5* 16* 12
20* 19* 18* 17 * 15 * 14 * 13/9* 7* 6* 5
317 444 400/1890
167 960

As we can see, the eighth and the twelfth terms have different coefficients. Thus, the given statement is false.

Alternative Solution

Alternative Solution
We can know the coefficients of (x+y)^(20) by finding the 20th row of the Pascal's triangle. Since the coefficients of the given binomial are both equal to 1, the coefficients in the triangle will be symmetric. In the20th row, there are21terms. The middle term will be the one in the 11th position and the row will be symmetric with respect to this coefficient.

From the above, we conclude that the eighth and the twelfth terms will have different coefficients. Thus, the given statement is false.