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Linear Equations

Linear Equations are mathematical expressions of anything that proceeds without varying, shifting or altering direction along its track or path.

They are first-degree polynomials and graph as straight lines. Their variables do not appear in the denominator of a fraction and have an exponent of 1:

4x - 12 = 16 is an example.

If a linear equation solution is two variables it provides Cartesian Coordinates, (x, y), to graph a straight line that is sloping, horizontal or vertical. Multiple lines on a Cartesian coordinate system diagram can be parallel or intersecting. A straight line requires at least 2 coordinates, each specifies a unique point on that line.

Sometimes “Rectangular” is used instead of Cartesian, as; Rectangular Coordinate System, Rectangular Coordinates.

Single Variable Linear Equations

Are solved by isolating one variable onto one side of the equation:

2(3y - 1) = 4(y - 5)

6y - 2 = 4y - 20

6y - 4y = 2 - 20

2y = -18

y = -9

2x/4 = 3(x - 4)/2 =

4 (2x / 4) = 4 [3 (x - 4) / 2]

2x = 2 [3 (x - 4)]

2x = 6x - 24

x = (6x - 24) / 2

x = 3x - 12

x - 3x = -12

-2x = -12

x = 6

0.4 x + 0.37 = 0.21x - 4

100 (0.4 x + 0.37) = 100 (0.21x - 4)

40x + 37 = 21x - 400

40x - 21x = -400 - 37

19x = -437

x = -23

Linear Equation Word Problems

(Creating equations to solve linear problems.)

A formula for velocity is: V = K + 32t; where V is velocity, K is energy and t is time:

V - K = 32t

(V - K)/32 = t

Cut a pipe that is 21 feet long so that one piece is twice the length of the other:

p + 2p = 21

3p = 21

p = 7

The shorter pipe is 7 feet. The longer piece is 14 feet.

7 + 14 = 21

The sum of two numbers is 17. Find the numbers if twice the smaller is 4 more than the larger:

x + 2x - 4 = 17

3x = 21

x = 7 is the smaller number.

2x - 4 = 14 - 4 = 10 is the larger number.

Help: First break the problem into components then solve it;

State the equation as f(g) + f(h) = 17 then define f(g) and f(h).

f(g) = x, the smaller number.

f(h) = 2x - 4, second number is four less twice the smaller number.

f(g) + f(h) = 17 = x + 2x - 4