If a, b, c \in R and a^2 + b^2 + c^2 + 4 = ab + bc + 2c + 2a, then roots of ax^2 + bx + c = 0 are:
Step-by-Step Solution
Key Concept: Sum of squares identity to find specific values of a, b, c
Step 1: Rearrange the given equation to standard form.
We start with the given condition:
$$a^2 + b^2 + c^2 + 4 = ab + bc + 2c + 2a$$
Moving all terms to one side:
$$a^2 + b^2 + c^2 + 4 - ab - bc - 2c - 2a = 0$$
Step 2: Multiply the equation by 2 to facilitate grouping into perfect squares.
Multiplying both sides by 2:
$$2a^2 + 2b^2 + 2c^2 + 8 - 2ab - 2bc - 4c - 4a = 0$$
Step 3: Regroup the terms to express them as sums of perfect squares.
We strategically rearrange the terms:
$$2a^2 + 2b^2 + 2c^2 + 8 - 2ab - 2bc - 4c - 4a$$
$$= (a^2 - 2ab + b^2) + (b^2 - 2bc + c^2) + (a^2 - 4a + 4) + (c^2 - 4c + 4)$$
Step 4: Express each group as a perfect square.
Recognizing the perfect square patterns:
$$(a - b)^2 + (b - c)^2 + (a - 2)^2 + (c - 2)^2 = 0$$
Step 5: Use the property that a sum of non-negative terms equals zero.
Since each squared term is non-negative (being a perfect square), and their sum equals zero, each term must individually equal zero:
$$(a - b)^2 = 0 \implies a = b$$
$$(b - c)^2 = 0 \implies b = c$$
$$(a - 2)^2 = 0 \implies a = 2$$
$$(c - 2)^2 = 0 \implies c = 2$$
Therefore: $a = b = c = 2$
Step 6: Form the quadratic equation with the found values.
Substituting $a = 2$, $b = 2$, and $c = 2$ into $ax^2 + bx + c = 0$:
$$2x^2 + 2x + 2 = 0$$
Dividing by 2:
$$x^2 + x + 1 = 0$$
Step 7: Calculate the discriminant to determine the nature of roots.
For the quadratic $x^2 + x + 1 = 0$, the discriminant is:
$$\Delta = b^2 - 4ac = (1)^2 - 4(1)(1) = 1 - 4 = -3$$
Since $\Delta = -3 < 0$, the roots are complex (imaginary).
**Final Answer:** The roots of $ax^2 + bx + c = 0$ are **imaginary**.
The correct option is **Option 3: imaginary**.
Correct Answer: 3