Why Are There No Real Solutions to the Equation \( |x^2 + 4x| = -12 \)?

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SUMMARY

The equation \( |x^2 + 4x| = -12 \) has no real solutions due to the properties of absolute values, which are always non-negative. Algebraically, the analysis involves two cases: when \( x^2 + 4x \ge 0 \) leading to \( x^2 + 4x + 12 = 0 \) and when \( x^2 + 4x < 0 \) resulting in \( -x^2 - 4x + 12 = 0 \). In both cases, the discriminant must be evaluated, confirming that no real solutions exist as absolute values cannot be negative.

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Explain why there are no real numbers that satisfy the equation
$$|x^2 + 4x| = - 12$$
How is this done algebraically?
 
Last edited by a moderator:
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RTCNTC said:
Explain why there are no real numbers that satisfy the equation

|x^2 + 4x| = - 12

because ...

$|\text{whatever}| \ge 0$

How is this done algebraically?

solve each case ...

case 1 ... $x^2+4x \ge 0 \implies x^2+4x+12 = 0$ ... recommend looking at the discriminant

case 2 ... $x^2+4x < 0 \implies -x^2-4x+12 = 0$ ... check the two real solutions in the original abs equation.
 

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$|whatever| \ge 0 \implies |whatever| \nless 0$

... that's it.
 
Great. We now move on to the next topic.
 

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