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The distance between the points $A$ and $B$ is $\sqrt{5}.$ If $A = (a,-1)$ and $B = (2,2a-1),$ then find the sum of all possible values of $a.$

2 Answers

4 votes

Final answer:

The sum of all possible values of $a$ is $\frac{8}{5}$.

Step-by-step explanation:

To find the sum of all possible values of $a$, we first need to find the distance between points $A$ and $B$ using the distance formula.

The distance formula is given by:

\(d = \sqrt{ (x_2 - x_1)^2 + (y_2 - y_1)^2 }\)

Using the given coordinates for points $A$ and $B$, we have:

\(d = \sqrt{(2 - a)^2 + (2a - 1 + 1)^2}\)

Expanding and simplifying the expression, we get:

\(d = \sqrt{a^2 - 4a + 4 + 4a^2 - 4a + 1}\)

\(d = \sqrt{5a^2 - 8a + 5}\)

Since the distance between points $A$ and $B$ is given as $\sqrt{5}$, we can equate the expression obtained above to $\sqrt{5}$ and solve for $a$:

\(\sqrt{5a^2 - 8a + 5} = \sqrt{5}\)

Squaring both sides of the equation, we get:

\(5a^2 - 8a + 5 = 5\)

Simplifying further, we have:

\(5a^2 - 8a = 0\)

Factoring out $a$, we get:

\(a(5a - 8) = 0\)

Setting each factor equal to zero and solving, we find two possible values for $a$: $a = 0$ and $a = \frac{8}{5}$.

Therefore, the sum of all possible values of $a$ is $0 + \frac{8}{5} = \frac{8}{5}$.

User Silk
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7.9k points
3 votes


{(2a - 1)^(2) - (2 - a)^2} = {5}Answer:

0.8

Step-by-step explanation:


\sqrt{((2a - 1) - (-1))^(2) + (2 - a)^2} = √(5) (distance equation)


{(2a)^(2) + (2 - a)^2} = {5} (squaring both sides)


{4a^(2) + 4 - 4a + a^2} = {5} (expanding the squares)


{5a^(2) - 4a - 1} = {0} (Collecting like terms)

Through the quadratic formula:

a1 = 1\\a2 = -0.2 \\a1 + a2 = 0.8

User Neocotic
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7.3k points