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The number of real roots for the eqiuati...

The number of real roots for the eqiuation `x^(2) + 9 | x| + 20 = 0 ` is

A

Zero

B

One

C

Two

D

Three

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The correct Answer is:
To determine the number of real roots for the equation \( x^2 + 9 |x| + 20 = 0 \), we will analyze the equation by considering the two cases for the absolute value function. ### Step 1: Split the equation based on the absolute value. The absolute value function \( |x| \) behaves differently based on the sign of \( x \): - If \( x \geq 0 \), then \( |x| = x \). - If \( x < 0 \), then \( |x| = -x \). ### Step 2: Case 1 - When \( x \geq 0 \) In this case, we replace \( |x| \) with \( x \): \[ x^2 + 9x + 20 = 0 \] Now, we will factor this quadratic equation. ### Step 3: Factor the quadratic equation We need two numbers that multiply to \( 20 \) and add up to \( 9 \). The numbers \( 5 \) and \( 4 \) satisfy this condition: \[ (x + 5)(x + 4) = 0 \] Setting each factor to zero gives: \[ x + 5 = 0 \quad \Rightarrow \quad x = -5 \] \[ x + 4 = 0 \quad \Rightarrow \quad x = -4 \] ### Step 4: Check the validity of the roots Since we are in the case where \( x \geq 0 \), both roots \( -5 \) and \( -4 \) are not valid because they are negative. Thus, there are no real roots from this case. ### Step 5: Case 2 - When \( x < 0 \) In this case, we replace \( |x| \) with \( -x \): \[ x^2 - 9x + 20 = 0 \] Now, we will factor this quadratic equation. ### Step 6: Factor the quadratic equation We need two numbers that multiply to \( 20 \) and add up to \( -9 \). The numbers \( -5 \) and \( -4 \) satisfy this condition: \[ (x - 5)(x - 4) = 0 \] Setting each factor to zero gives: \[ x - 5 = 0 \quad \Rightarrow \quad x = 5 \] \[ x - 4 = 0 \quad \Rightarrow \quad x = 4 \] ### Step 7: Check the validity of the roots Since we are in the case where \( x < 0 \), both roots \( 5 \) and \( 4 \) are not valid because they are positive. Thus, there are no real roots from this case either. ### Conclusion Since both cases yield no valid real roots, the equation \( x^2 + 9 |x| + 20 = 0 \) has **no real roots**. ### Final Answer The number of real roots for the equation is **0**. ---

To determine the number of real roots for the equation \( x^2 + 9 |x| + 20 = 0 \), we will analyze the equation by considering the two cases for the absolute value function. ### Step 1: Split the equation based on the absolute value. The absolute value function \( |x| \) behaves differently based on the sign of \( x \): - If \( x \geq 0 \), then \( |x| = x \). - If \( x < 0 \), then \( |x| = -x \). ### Step 2: Case 1 - When \( x \geq 0 \) ...
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