Find the sum of all values of a such that the point, (a,7) is 3sqrt5 from the point (2,1)

Question

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Answer 1

√[(a-2)² + (7-1)²] = 3√5

 

√(a² - 4a + 40) = 3√5

 

a² - 4a + 40 = 45

 

a² - 4a - 5 = 0

 

(a-5)(a+1) = 0

 

a = 5 or a = -1

 

sum of values of a = -1 + 5 = 4