Math  /  Algebra

Question6. Find the positive value of xx that solves the following equation: x=k=030(30k)2030kx^{\infty}=\sum_{k=0}^{30}\binom{30}{k} 20^{30-k}
ANS: \qquad

Studdy Solution

STEP 1

1. The equation involves an infinite power, x x^{\infty} , which implies that x x must be 1 for the expression to be finite and non-zero.
2. The right-hand side of the equation is a finite sum involving binomial coefficients and powers of 20.

STEP 2

1. Analyze the left-hand side of the equation.
2. Analyze the right-hand side of the equation.
3. Determine the value of x x .

STEP 3

Analyze the left-hand side of the equation x x^{\infty} .
If x x^{\infty} is finite and non-zero, then x x must be equal to 1. This is because any number greater than 1 raised to the power of infinity becomes infinite, and any number less than 1 raised to the power of infinity becomes zero.

STEP 4

Analyze the right-hand side of the equation:
The right-hand side is a finite sum given by:
k=030(30k)2030k \sum_{k=0}^{30} \binom{30}{k} 20^{30-k}
This expression represents the expansion of (1+20)30 (1 + 20)^{30} using the binomial theorem, which states:
(a+b)n=k=0n(nk)ankbk (a + b)^n = \sum_{k=0}^{n} \binom{n}{k} a^{n-k} b^k
Here, a=1 a = 1 , b=20 b = 20 , and n=30 n = 30 , so:
(1+20)30=2130 (1 + 20)^{30} = 21^{30}

STEP 5

Determine the value of x x :
Since x=2130 x^{\infty} = 21^{30} and x x^{\infty} is finite and non-zero, x x must be equal to 1.
Therefore, the positive value of x x that satisfies the equation is:
1 \boxed{1}

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