AMU 2026 — Mathematics PYQ
AMU | Mathematics | 2026The values of satisfying the equation are:

The values of x satisfying the equation ∣(x4−4)−(x2+2)∣=∣x4−4∣−∣x2+2∣ are:
(−∞,−3)∪(3,∞)
(−∞,−3)∪[3,∞)
(Correct Answer)(−∞,−3)∪(3,∞)
(−∞,−3]∪[3,∞)
(−∞,−3)∪[3,∞)
To solve this equation efficiently, let's substitute the complex algebraic expressions with simpler variables. Let:
a=x4−4
b=x2+2
Now substitute a and b back into the original given equation:
∣a−b∣=∣a∣−∣b∣
According to the fundamental properties of absolute values, the property ∣a−b∣=∣a∣−∣b∣ holds true if and only if:
a and b have the same sign (or a is zero), meaning a⋅b≥0.
The absolute value of a is greater than or equal to the absolute value of b, meaning ∣a∣≥∣b∣.
Equivalently, this condition simplifies directly to:
a⋅b≥0and∣a∣≥∣b∣
Since b=x2+2, we know that for any real value of x, x2≥0, which means b≥2. Since b is strictly positive (b > 0), for the condition to hold, a must be non-negative and greater than or equal to b:
a≥b
Substitute the expressions for a and b back into the simplified condition a≥b:
x4−4≥x2+2
Move all terms to the left-hand side to form a quadratic-style polynomial inequality:
x4−x2−4−2≥0
x4−x2−6≥0
Let y=x2. The inequality turns into a standard quadratic equation layout:
y2−y−6≥0
Factor the quadratic equation by splitting the middle term:
y2−3y+2y−6≥0
y(y−3)+2(y−3)≥0
(y−3)(y+2)≥0
Now, substitute x2 back in place of y:
(x2−3)(x2+2)≥0
Let's analyze the two factored components:
The term (x2+2) is always strictly positive (x2+2≥2) for all real values of x.
Because (x^2 + 2) > 0, we can divide both sides of the inequality by it without changing the direction of the inequality sign:
x2−3≥0
x2≥3
∣x∣≥3
This absolute value inequality expands into the following intervals on a number line:
x≤−3orx≥3
Expressed in standard interval notation:
x∈(−∞,−3]∪[3,∞)
To solve this equation efficiently, let's substitute the complex algebraic expressions with simpler variables. Let:
a=x4−4
b=x2+2
Now substitute a and b back into the original given equation:
∣a−b∣=∣a∣−∣b∣
According to the fundamental properties of absolute values, the property ∣a−b∣=∣a∣−∣b∣ holds true if and only if:
a and b have the same sign (or a is zero), meaning a⋅b≥0.
The absolute value of a is greater than or equal to the absolute value of b, meaning ∣a∣≥∣b∣.
Equivalently, this condition simplifies directly to:
a⋅b≥0and∣a∣≥∣b∣
Since b=x2+2, we know that for any real value of x, x2≥0, which means b≥2. Since b is strictly positive (b > 0), for the condition to hold, a must be non-negative and greater than or equal to b:
a≥b
Substitute the expressions for a and b back into the simplified condition a≥b:
x4−4≥x2+2
Move all terms to the left-hand side to form a quadratic-style polynomial inequality:
x4−x2−4−2≥0
x4−x2−6≥0
Let y=x2. The inequality turns into a standard quadratic equation layout:
y2−y−6≥0
Factor the quadratic equation by splitting the middle term:
y2−3y+2y−6≥0
y(y−3)+2(y−3)≥0
(y−3)(y+2)≥0
Now, substitute x2 back in place of y:
(x2−3)(x2+2)≥0
Let's analyze the two factored components:
The term (x2+2) is always strictly positive (x2+2≥2) for all real values of x.
Because (x^2 + 2) > 0, we can divide both sides of the inequality by it without changing the direction of the inequality sign:
x2−3≥0
x2≥3
∣x∣≥3
This absolute value inequality expands into the following intervals on a number line:
x≤−3orx≥3
Expressed in standard interval notation:
x∈(−∞,−3]∪[3,∞)