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The number of solution to the equation ∣x∣(6x2+1)=5x2|x|(6x^2 + 1) = 5x^2 is

Entered answer:

Solution

✅ Correct Answer: 5

Since we have ∣x∣|x|, we need to consider:

When x>0x > 0, then ∣x∣=x|x| = x

When x<0x < 0, then ∣x∣=−x|x| = -x

When x=0x = 0, then ∣x∣=0|x| = 0

The absolute value ∣x∣|x| behaves differently depending on whether xx is positive or negative, so we must handle each situation separately.


If x>0x > 0, then ∣x∣=x|x| = x

x(6x2+1)=5x2x(6x^2 + 1) = 5x^2

6x3+x=5x26x^3 + x = 5x^2

6x3−5x2+x=06x^3 - 5x^2 + x = 0

x(6x2−5x+1)=0x(6x^2 - 5x + 1) = 0

Now we need to factor 6x2−5x+16x^2 - 5x + 1.

6x2−5x+1=6x2−2x−3x+16x^2 - 5x + 1 = 6x^2 - 2x - 3x + 1

=2x(3x−1)−1(3x−1)= 2x(3x - 1) - 1(3x - 1)

=(2x−1)(3x−1)= (2x - 1)(3x - 1)

So our equation becomes:

x(2x−1)(3x−1)=0x(2x - 1)(3x - 1) = 0

This gives us: x=0x = 0, x=12x = \dfrac{1}{2}, or x=13x = \dfrac{1}{3}

Since we assumed x>0x > 0, we must verify which solutions are valid:

x=0x = 0 does NOT satisfy x>0x > 0, so we reject this

Valid solutions from Case 1: x=12,13x = \dfrac{1}{2}, \dfrac{1}{3}


If x<0x < 0, then ∣x∣=−x|x| = -x

−x(6x2+1)=5x2-x(6x^2 + 1) = 5x^2

−6x3−x=5x2-6x^3 - x = 5x^2

−6x3−5x2−x=0-6x^3 - 5x^2 - x = 0

−x(6x2+5x+1)=0-x(6x^2 + 5x + 1) = 0

Since we're considering x<0x < 0, we have −x>0-x > 0, so:

6x2+5x+1=06x^2 + 5x + 1 = 0

6x2+5x+1=6x2+2x+3x+16x^2 + 5x + 1 = 6x^2 + 2x + 3x + 1

=2x(3x+1)+1(3x+1)= 2x(3x + 1) + 1(3x + 1)

=(2x+1)(3x+1)= (2x + 1)(3x + 1)

So: (2x+1)(3x+1)=0(2x + 1)(3x + 1) = 0

This gives us: x=−12x = -\dfrac{1}{2} or x=−13x = -\dfrac{1}{3}

Both values satisfy x<0x < 0

Valid solutions from Case 2: x=−12,−13x = -\dfrac{1}{2}, -\dfrac{1}{3}


Let's check if x=0x = 0 satisfies our original equation:

∣0∣(6(0)2+1)=5(0)2|0|(6(0)^2 + 1) = 5(0)^2

0⋅1=00 \cdot 1 = 0

0=00 = 0

Valid solution from Case 3: x=0x = 0


Combining all valid solutions:

From Case 1: x=12,13x = \dfrac{1}{2}, \dfrac{1}{3}

From Case 2: x=−12,−13x = -\dfrac{1}{2}, -\dfrac{1}{3}

From Case 3: x=0x = 0

Total number of solutions: 5

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