The terms consistent and dependent are two ways to describe a system of linear equations. A system of linear equations is dependent if you can algebraically derive one of the equations from one or more of the other equations. A system of linear equations is consistent if they have a common solution.
An example of a dependent system of linear equations:
2x + 4y = 8
4x + 8y = 16
Solve the first equation for x:
x = 4 - 2y
Plug that value of x into the second equation:
16 - 8y + 8y = 16, which gives 16 = 16.
No new information was gained from the second equation, because we already knew 16 = 16, so these two equations are dependent.
An example of an inconsistent system of linear equations:
Because consistency is boring.
2x + 4y = 8
4x + 8y = 15
Solve the first equation for x:
x = 4 - 2y
Plug that value of x into the second equation:
16 - 8y + 8y = 15, which gives 16 = 15.
This is a contradiction, because 16 doesn't equal 15. Therefore this system has no solution and is inconsistent.
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It has more than one solutions.
The equations are consistent and dependent with infinite solution if and only if a1 / a2 = b1 / b2 = c1 / c2.
Suppose we have two linear equations in two unknowns. If the equations are plotted on a rectangular grid, the graph will fit one of these scenarios: 1) The two lines cross each other (intersect). 2) The two lines don't cross - they are parallel lines 3) The two lines fall on top of each other - they're really the same line. In case 3) the two lines are dependent - one can be changed into the other. In cases 1) and 2) we say the lines are independent. If the pair of equations has a solution (one or more points in common) we say they are consistent ... cases 1) and 3). In case 2) the system is inconsistent; there is no solution. To summarize: 1) Intersecting lines are consistent and independent. 2) Parallel lines are inconsistent and independent. 3) Coincident ["happen together"] lines are consistent and dependent. *** A second order linear system CANNOT be both dependent and inconsistent.
That doesn't apply to "an" equation, but to a set of equations (2 or more). Two equations are:* Inconsistent, if they have no common solution (a set of values, for the variables, that satisfies ALL the equations in the set). * Consistent, if they do. * Dependent, if one equation can be derived from the others. In this case, this equation doesn't provide any extra information. As a simple example, one equation is the same as another equation, multiplying both sides by a constant. * Independent, if this is not the case.
The dependent variable is dependent on the independent variable, so when the independent variable changes, so does the dependent variable.