Solved on Dec 05, 2023

Solve 7x2+1=4x7 x^{2} + 1 = -4 x over complex numbers. Solution set is x=1±12814x = \frac{-1 \pm \sqrt{1 - 28}}{14}.

STEP 1

Assumptions
1. We are solving the quadratic equation 7x2+1=4x7x^{2} + 1 = -4x.
2. The solutions are to be found over the set of complex numbers.

STEP 2

To solve the quadratic equation, we first need to bring all terms to one side of the equation to set it equal to zero.
7x2+4x+1=07x^{2} + 4x + 1 = 0

STEP 3

Now we will attempt to factor the quadratic, but if that is not possible, we will use the quadratic formula to find the roots. The quadratic formula is given by:
x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}
where aa, bb, and cc are the coefficients of the quadratic equation ax2+bx+c=0ax^2 + bx + c = 0.

STEP 4

Identify the coefficients aa, bb, and cc from the quadratic equation 7x2+4x+1=07x^{2} + 4x + 1 = 0.
a=7,b=4,c=1a = 7, b = 4, c = 1

STEP 5

Plug the coefficients aa, bb, and cc into the quadratic formula.
x=4±4247127x = \frac{-4 \pm \sqrt{4^2 - 4 \cdot 7 \cdot 1}}{2 \cdot 7}

STEP 6

Simplify the expression under the square root (the discriminant).
Δ=42471=1628=12\Delta = 4^2 - 4 \cdot 7 \cdot 1 = 16 - 28 = -12

STEP 7

Since the discriminant Δ\Delta is negative, we will have two complex roots. We can express the square root of a negative number using the imaginary unit ii where i2=1i^2 = -1.
12=12i=23i\sqrt{-12} = \sqrt{12} \cdot i = 2\sqrt{3} \cdot i

STEP 8

Substitute the value of the discriminant back into the quadratic formula.
x=4±23i14x = \frac{-4 \pm 2\sqrt{3} \cdot i}{14}

STEP 9

Simplify the fraction by dividing both the numerator and the denominator by 2.
x=2±3i7x = \frac{-2 \pm \sqrt{3} \cdot i}{7}

STEP 10

Now we have the two solutions for the quadratic equation, which are complex numbers.
x1=2+3i7x_1 = \frac{-2 + \sqrt{3} \cdot i}{7} x2=23i7x_2 = \frac{-2 - \sqrt{3} \cdot i}{7}
The solution set is {2+3i7,23i7}\left\{ \frac{-2 + \sqrt{3} \cdot i}{7}, \frac{-2 - \sqrt{3} \cdot i}{7} \right\}.

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