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4 votes
Find the value of the lesser root of x2 - 8x + 7 = 0.

A) -1


B) 1


C) 3


D) 5

2 Answers

7 votes

Answer:

x = 1

Explanation:

Please express exponentiation using the symbol " ^ " : x^2 - 8x + 7 = 0

Let's solve this equations using "completing the square:"

x^2 - 8x + 7 = 0

1) Identify the coefficient of the x term. Here it's -8.

2) take half of that and square it: we get (-4)² = 16

3) insert " +16 - 16 " between the 8x and the 7:

x^2 - 8x + 16 - 16 +7 = 0

4) Rewrite this perfect square:

(x - 4)² - 16 + 7 = 0 -> (x - 4)^2 = 9

5) Solve for (x -4) by taking the square root of both sides:

x - 4 ± sqrt(9) -> x - 4 ± 3

6) Solve for x: x = 4 ± 3, or x = 7 and x = 1.

7) Take the lesser root of 7 and 1. That would be x = 1. Answer B is correct.

User Michael Borgwardt
by
7.7k points
1 vote

Answer:

B) 1.

Explanation:

x^2 - 8x + 7 = 0

(x - 1)(x - 7) = 0

x= 1, 7.

User Ceebreenk
by
9.3k points

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