These **numerous mathematical resources (calculators, quizzes, games, exercises) allow to practice solving equations**.

- Countdown solver : arithmetic_solver. This countdown solver allows finding a target number from a set of integer in using arithmetic operations.
- Solving quadratic equation with complex number : complexe_solve. The complex number equation calculator returns the complex values for which the quadratic equation is zero.
- Calculation of the discriminant online : discriminant. Calculator that allows the calculation of the discriminant of a quadratic equation online.
- Solve for x calculator : equation_solver. The equation solver allows to solve equations with an unknown with calculation steps : linear equation, quadratic equation, logarithmic equation, differential equation.
- Find equation of a straight line from two points : equation_straight_line. The equation straight line calculator allows to calculate the equation of a straight line from the coordinates of two points with step by step calculation.
- Find the equation of tangent line : equation_tangent_line. The tangent line equation calculator is used to calculate the equation of tangent line to a curve at a given abscissa point with stages calculation.
- Inequality calculator : inequality_solver. Inequality solver that solves an inequality with the details of the calculation: linear inequality, quadratic inequality.
- Pythagorean theorem calculator : pythagorean. The calculator uses the Pythagorean theorem to verify that a triangle is right-angled or to find the length of one side of a right-angled triangle.
- Solve system of linear equations : solve_equations. The solver of systems of linear equations allows to solve equations with several unknowns: system of equations with 2 unknowns, system of equations with 3 unknowns, system with n unknowns.

- Quiz solving equations of the second degree : This quiz on the equations of the second degree allows to practice the methods of resolution based on the use of the discriminant.
- Quiz solving equations with one unknown : This quiz on equations allows to practice solving different types of equations with one unknown.
- Quiz solving first degree equations : This quiz on first degree equations allows to practice solving simple equations with one unknown.

An **equation is an equality that involves one or more variables**, solving an equation in a set is to find the value or values of the variables in that set that verify the equation,
these are the solutions of the equation. The variables are often referred to as the unknown,
when the equation has only one unknown, it is often referred to as x.

For example, 3x-3=0 is an equation, solving for x in ℝ this equation is to find the solutions in ℝ of this equation.

When we have to solve several equations, with several variables, we speak of a system of equations.

There are **methods and formulas for solving certain types of equations** such as first degree equations (linear equation),
second degree equations (quadratic equation), or product equations.

### Solve an equation with one unknown of the first degree

- When we add or subtract the same real to both members of an equation, we obtain a new equation which has the same solutions as the previous one.
- When we multiply or divide the two members of an equation by a non-zero real, we obtain a new equation that has the same solutions as the previous one.
### Solving a product equation

- Saying that a.b = 0 is equivalent to saying that a is zero or that b is zero.
- Think of using the special expansions to get back to a product of factors and a classic case of solving an equation.
### Solve a second degree equation using the discriminant

- When `Delta<0` the equation has no root
- When `Delta=0` the equation has a root `-b/2a`
- When `Delta>0` the equation has two distinct roots `(-b-sqrt(Delta))/(2a)` and `(-b+sqrt(Delta))/(2a)`

**Solving an equation with one unknown** x in R, it is to determine the set of real numbers x verifying the said equation.
This set is called the set of solutions of the equation.

A product of two factors is zero if and only if one of the factors is zero.

We call the discriminant of the trinomial `a*x^2+b*x+c`, with a not zero, the real `Delta=b^2-4*a*c`.

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