Mister Exam
Other calculators
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How to use it?
- Equation:
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Equation 2*x^2-x+5=0
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Equation e^x=1
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Equation x^2+2=x+2
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Equation 5=12-5(4x-1)
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Identical expressions
- x^ two + three *x+ eighteen = zero
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- x to the power of two plus three multiply by x plus eighteen equally zero
- x2+3*x+18=0
- x²+3*x+18=0
- x to the power of 2+3*x+18=0
- x^2+3x+18=0
- x2+3x+18=0
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Similar expressions
- x^2+3*x-18=0
- x^2-3*x+18=0
x^2+3*x+18=0 equation
The teacher will be very surprised to see your correct solution 😉
The solution
Detail solution
This equation is of the form
A quadratic equation can be solved
using the discriminant.
The roots of the quadratic equation:
$$x_{1} = \frac{\sqrt{D} - b}{2 a}$$
$$x_{2} = \frac{- \sqrt{D} - b}{2 a}$$
where D = b^2 - 4*a*c - it is the discriminant.
Because
$$a = 1$$
$$b = 3$$
$$c = 18$$
, then
Because D<0, then the equation
has no real roots,
but complex roots is exists.
or
$$x_{1} = - \frac{3}{2} + \frac{3 \sqrt{7} i}{2}$$
$$x_{2} = - \frac{3}{2} - \frac{3 \sqrt{7} i}{2}$$
a*x^2 + b*x + c = 0
A quadratic equation can be solved
using the discriminant.
The roots of the quadratic equation:
$$x_{1} = \frac{\sqrt{D} - b}{2 a}$$
$$x_{2} = \frac{- \sqrt{D} - b}{2 a}$$
where D = b^2 - 4*a*c - it is the discriminant.
Because
$$a = 1$$
$$b = 3$$
$$c = 18$$
, then
D = b^2 - 4 * a * c =
(3)^2 - 4 * (1) * (18) = -63
Because D<0, then the equation
has no real roots,
but complex roots is exists.
x1 = (-b + sqrt(D)) / (2*a)
x2 = (-b - sqrt(D)) / (2*a)
or
$$x_{1} = - \frac{3}{2} + \frac{3 \sqrt{7} i}{2}$$
$$x_{2} = - \frac{3}{2} - \frac{3 \sqrt{7} i}{2}$$
Vieta's Theorem
it is reduced quadratic equation
$$p x + q + x^{2} = 0$$
where
$$p = \frac{b}{a}$$
$$p = 3$$
$$q = \frac{c}{a}$$
$$q = 18$$
Vieta Formulas
$$x_{1} + x_{2} = - p$$
$$x_{1} x_{2} = q$$
$$x_{1} + x_{2} = -3$$
$$x_{1} x_{2} = 18$$
$$p x + q + x^{2} = 0$$
where
$$p = \frac{b}{a}$$
$$p = 3$$
$$q = \frac{c}{a}$$
$$q = 18$$
Vieta Formulas
$$x_{1} + x_{2} = - p$$
$$x_{1} x_{2} = q$$
$$x_{1} + x_{2} = -3$$
$$x_{1} x_{2} = 18$$
Rapid solution
[src]
___
3 3*I*\/ 7
x1 = - - - ---------
2 2
$$x_{1} = - \frac{3}{2} - \frac{3 \sqrt{7} i}{2}$$
___
3 3*I*\/ 7
x2 = - - + ---------
2 2
$$x_{2} = - \frac{3}{2} + \frac{3 \sqrt{7} i}{2}$$
x2 = -3/2 + 3*sqrt(7)*i/2
Sum and product of roots
[src]
sum
___ ___ 3 3*I*\/ 7 3 3*I*\/ 7 - - - --------- + - - + --------- 2 2 2 2
$$\left(- \frac{3}{2} - \frac{3 \sqrt{7} i}{2}\right) + \left(- \frac{3}{2} + \frac{3 \sqrt{7} i}{2}\right)$$
=
-3
$$-3$$
product
/ ___\ / ___\ | 3 3*I*\/ 7 | | 3 3*I*\/ 7 | |- - - ---------|*|- - + ---------| \ 2 2 / \ 2 2 /
$$\left(- \frac{3}{2} - \frac{3 \sqrt{7} i}{2}\right) \left(- \frac{3}{2} + \frac{3 \sqrt{7} i}{2}\right)$$
=
18
$$18$$
18
Numerical answer
[src]
x1 = -1.5 + 3.96862696659689*i
x2 = -1.5 - 3.96862696659689*i
x2 = -1.5 - 3.96862696659689*i
The graph