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If the quadratic expression x^(2)-(a-1)x...

If the quadratic expression `x^(2)-(a-1)x+(a+(1)/(4))` were to be a perfect square then a=

A

0, 6

B

2, 4

C

1, 8

D

4, 8

Text Solution

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The correct Answer is:
To determine the values of \( a \) for which the quadratic expression \[ x^2 - (a-1)x + \left(a + \frac{1}{4}\right) \] is a perfect square, we will follow these steps: ### Step 1: Identify the form of a perfect square A quadratic expression \( x^2 + bx + c \) is a perfect square if it can be expressed as \( (x - p)^2 \) for some \( p \). This expands to: \[ x^2 - 2px + p^2 \] ### Step 2: Compare coefficients From the expression \( x^2 - (a-1)x + \left(a + \frac{1}{4}\right) \), we can compare coefficients with \( x^2 - 2px + p^2 \): - Coefficient of \( x \): \( -(a - 1) = -2p \) - Constant term: \( a + \frac{1}{4} = p^2 \) ### Step 3: Solve for \( p \) From the first equation, we can express \( p \): \[ a - 1 = 2p \implies p = \frac{a - 1}{2} \] ### Step 4: Substitute \( p \) into the second equation Substituting \( p \) into the second equation gives: \[ a + \frac{1}{4} = \left(\frac{a - 1}{2}\right)^2 \] ### Step 5: Simplify the equation Expanding the right side: \[ \left(\frac{a - 1}{2}\right)^2 = \frac{(a - 1)^2}{4} = \frac{a^2 - 2a + 1}{4} \] Setting the two sides equal: \[ a + \frac{1}{4} = \frac{a^2 - 2a + 1}{4} \] ### Step 6: Clear the fraction Multiply through by 4 to eliminate the fraction: \[ 4a + 1 = a^2 - 2a + 1 \] ### Step 7: Rearrange the equation Rearranging gives us: \[ a^2 - 2a - 4a + 1 - 1 = 0 \implies a^2 - 6a = 0 \] ### Step 8: Factor the quadratic Factoring out \( a \): \[ a(a - 6) = 0 \] ### Step 9: Solve for \( a \) Setting each factor to zero gives: \[ a = 0 \quad \text{or} \quad a = 6 \] ### Conclusion The values of \( a \) for which the quadratic expression is a perfect square are: \[ \boxed{0 \text{ and } 6} \]
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