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JEE Main 2026 Preparation: Question Papers, Solutions, Mock Tests & Strategy Unacademy » JEE Study Material » Mathematics » Identical and Linear Functions

Identical and Linear Functions

A linear function is defined as a function with one or two variables and no exponents in mathematics. It's a graphing function for the straight line.

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A linear function is a graph function that produces a straight line. It is usually a polynomial function with a maximum degree of 1 or 0. Although linear functions may be expressed in terms of both calculus and linear algebra. The function notation is the sole change.  P is the y-intercept or constant term, as well as the value of the dependent variable. When x = 0, q is the slope coefficient of the independent variable, which indicates the dependent variable’s rate of change.

Definition of linear and identical functions

A linear function is an algebraic equation in which each component is a constant or the sum of a constant and a single variable (the first power of). For example, the equation y=mx+b (also known as the slope-intercept form, which we shall discuss later) is a linear function since it fits both conditions using the variables x and y and the constants m and b. It is linear: the x term’s exponent is one (first power), and it follows the definition of a function: there is precisely one output for each input (x) (y). Its graph is also a straight line.

Graphs of Linear Functions

The word “linear” derives from the fact that the collection of solutions to such an equation forms a straight line in space. The constant mm defines the slope or gradient of the line in the graphs below, and the constant term bb determines the point at which the line crosses the y-axis, also known as the y-intercept.

Vertical and Horizontal Lines

Because the vertical line crosses a value on the x-axis, cc, it cannot be written in the form y=mx+b, but must be stated as an equation of the type x=c for a constant c. The graph of the equation x=4, for example, has the same input value of 4 at all points on the line, but distinct output values, such as (4,-2),(4,0),(4,1),(4,5),(4,2),(4,0),(4,1),(4,5),(4,2),(4,0),(4,1),(4,5), etc. Vertical lines, on the other hand, are not functions since each input has several outputs.

Horizontal lines have no slope and are expressed as y=b, where b is the y-intercept. For all input values on the line, such as (-2,6),(0,6),(2,6),(6,6), etc., a graph of the equation y=6 contains the same output value of 6 for all input values on the line. Because the connection (set of points) has the property that each input is associated to exactly one output, horizontal lines ARE functions.

Slope

The slope of a line is a number that describes the line’s direction as well as its steepness in mathematics. The letter mm is frequently used to represent slope. Remember that a line’s slope-intercept form is y = mx + b. Putting a line’s equation into this form yields the line’s slope (m) and y-intercept (b). We’ll now look at how to compute m for a given line and how to interpret m.

If a line increases from left to right, it has a positive slope (m > 0).

If a line descends from left to right with a negative slope (m <0), it is declining. The slope of a horizontal line is zero, and the function is constant (y=c). The slope of a vertical line is indeterminate.

The absolute value of the slope is used to determine the steepness, or inclination, of a line. To put it another way, a line with a slope of

A line with a slope of -9 is steeper than one with a slope of 7.

Direct and Inverse Variation

A linear relationship exists between two variables in direct variation, but not between variables in inverse variation.

Direct Variation

Simply said, when the same thing happens to one variable, it also happens to the other, two variables are in direct variation. If x and y are in direct proportion, and x is doubled, y will be doubled as well. The two variables have a straight proportional relationship.

A toothbrush, for example, costs $22. Buying 55 toothbrushes costs 1010 dollars, but buying 1010 toothbrushes costs 2020 dollars. As a result, we may argue that the price is proportional to the value of toothbrushes.

A linear equation represents direct variation, which may be depicted by charting a line. We may give their relationship with: since we know the relationship between two values is constant.

Inverse Variation

The inverse of direct variation is inverse variation. In the instance of inverse variation, increasing one variable cause another to decrease. When one variable undergoes a change while the other undergoes the reverse, the two variables are said to be inversely proportional. If x and y are inversely proportionate, for example, if x is doubled, y is half.

The length of a voyage, for example, is inversely related to the pace of motion. The journey to your goal will be shorter if your automobile goes faster.

Conclusion 

In this article, we conclude that what are Linear functions, linear and identical functions are the same and characteristics of linear and identical functions. What are slopes and direct and inverse variations we hope that this article comes in hand to learn and solve the problems of liner functions. If the function has additional variables, the variables should be constant or known to keep the function in the same linear function condition. In this article, we’ll go over what a linear function is, as well as its table, graph, formulae, properties, and examples.

faq

Frequently asked questions

Get answers to the most common queries related to the JEE Examination Preparation.

How to find the equation of a line that passes through two points?

Answer. You had to represent the provided information as ordered pairs in several linear application problems, and t...Read full

How do you find the equation of a line?

Answer. In this FAQ, I’ll show you how to obtain line equations using y ...Read full

How Do I Deal With Variables Other Than x in Linear Functions?

Answer. Students frequently come across two issues while working with function...Read full

How Do You Find The Intercepts of a Linear Function?

Answer. The equation 25p + 21x = 1215 may be used to link the percent p of hig...Read full

Answer. You had to represent the provided information as ordered pairs in several linear application problems, and then discover the equation that passed across the ordered pairs. In this example, p = mt + b is used instead of y = mx + b.

Answer. In this FAQ, I’ll show you how to obtain line equations using y = mx + b. There’s no need to remember any additional line equations… It is simpler to concentrate on the information provided and apply it to determine m and b.

Let’s have a look at the most simple example of this technique.

1. Determine the equation of a line passing through the points (4, -6) and having a slope of – 3/4.

To get the slope-intercept form, start by putting m = -3/4.

y = – 3/4 x + b

Set x = 4 and y = -6 to substitute the point into the line. As a result,

In the slope-intercept form above, this value for b results in the line y = –3/4 x -3. The equation of the line with the suitable values for m and b is the solution to the issue.

Let’s make things a little more difficult by determining the equation of a line that passes through two points.

2. Draw a line connecting the locations (-1, 3) and (2, 6).

The angle between the points is

To get y = x + b, substitute the slope into the slope-intercept form.

Substitute one of the points into this equation. We can solve for b using the ordered pair (2, 6). We now get the equation y = x + 4.

Answer. Students frequently come across two issues while working with functions that have strange variable names and scaling.

Having problems figuring out what each variable means and problems with the variables’ scaling.

Answer. The equation 25p + 21x = 1215 may be used to link the percent p of high school seniors who have ever smoked marijuana to x, the number of years after 2000.

  1. Determine the x-intercepts of this function’s graph.
  2. Determine and explain the p intercept of this function’s graph.
  3. Use the intercept to graph the function.

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