Solving linear equation both in algebraic and geometric world

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    Solving Linear Equation

    Many people think that equations and algebra are obscure and use some esoteric languages. Truth is that equations are actually relatively simple concepts; knowing the base rules of the game and a bit of practice, you can learn to manipulate and solve them in a snap.

    Linear equation are the simplest form of equation you may deal with; it restrict the problem to a unique unknown variable (usually called ‘x’) and no exponent e.g.:

    x − 30 = 15

    We all have solve this kind of equation every day even without even notifying it. Let’s say I am currently getting a training, I just know it’s been 30 minutes I am running and the coach told us that we still remain 15 minutes running. How much are we gonna run in total? This problem can be written as the following:

    ?TotalTime? − TimeAlreadyRun = TimeLeftx − 30 = 15

    The result may already be solved, but let’s play the equation game:

    TotalTime= TimeAlreadyRun + TimeLeft = 30 + 15 = 45Minutes

    We know for sure we are gonna made a total 45 minutes run (except if the coach is playing on us). Now let’s have a peek to the rules of the game, you’ll see: there is quite few (even with the most complex problems)!

    Rules of the Game


    An equation is like a statement saying "this equals that”. The previous equation, x - 30 = 15 asks: what x will make makes this equation true?

    The goal is thus to find that x; in the algebraic world, meaning to end up with:
    x = something without x.

    Next part present you the unique rule and useful tools dedicated to reach this goal. Keep in mind that solving an equation is just like solving a puzzle: there are things we can do and some others that are forbidden.


    There is only two rules to satisfy:

    Whatever you do to one side of the equation, you must do to the other side.

    You are forbidden to divide anything by 0.

    Get there for the list of tools:

    Example of detailed resolution

    Equation Resolution

    Check your solution

    You should always check that your “solution” is really a solution, there is nothing more easy: Replace ‘x’ by the solution value within the equation and verify that the equality is true.

    Be careful to check that your solution never divide by 0!
    In the previous example we found x = 45. If we place it within the equation, we get: 45 − 30 = 15
    Which is true: the solution has been verified.

    The always winning method

    It’s not the optimal way, but the always winning robot always reach the goal using this method! Here is how he proceeds:

    Does the equation have fractions?
    Yes → Multiply every term (on both sides) by the denominator.

    Does the equation involve parenthesis?
    Yes → Expand the equation using the tools.

    On either side, does it have like terms?
    Yes → Combine like terms. (Don’t forget the sign in front of each term!)

    Does it have variables on both sides of the equation?
    Yes → Add or subtract the terms to get all the variables on the left side and all the constants on the right side.

    At this point, the robot has a basic two-step equation (If not, he would be bugged).

    Add or Subtract to remove any constants from the left side of the equation.
    Multiply or Divide to remove any coefficients form the left side of the equation.


    At the end, the robot does not forget to check its answer to detect any eventual problem :). See the robot in action step-by-step:

    Equations and Graph Representation

    Any linear expression (the left or right part of an equation) can be drawn as a line in a 2D graphic. The graph drawing is very simple. For each part of the equation, we have x on the horizontal axis and for a range of y values (vertical abscisse) we compute and plot the points (x, y).

    Constant line
    The easiest line, a constant: y=-3 (for all x, y = -3).

    alt text
    The other basic line to know: y=x (for all x, y as the same value).

    alt text
    Drawing here y = 2x
    Multiplying x by a constant is making a rotation on the line

    alt text
    Drawing here all together y = 2x - 3
    Adding or substracting the expression by a constant value is just adding an offset

    A linear equation can be then drawn as two lines crossing each other. The intersection point of those two lines is the equation solution (if the lines are parallel, it means that the equation does not have any solution). Indeed the question answer the same one from the algebraic world: What x will make makes this equation true, when are those lines equal?

    With our previous example:
    Resolving Linear Equation With Gra

    The advantage of drawing a graph of an equation is that you can then use it to visualize out the value of y for any given value of x, or indeed x for any given value of y.

    We have illustrated here the relationship between an algebraic equation and its graph plots giving you an alternative way to understand equations.

    Jump in Hurna Explorer to practice and visualize yourself any equations.

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