Buy BOOKS at Discounted Price

Graphs

Class 8th Mathematics RS Aggarwal Solution

Exercise 25a
Question 1.

On a graph paper draw the coordinate axes X’OX and YOY’, and plot each of the following points:

(i) (ii)

(iii) (iv)

(v) (vi)

(vii) (viii)


Answer:

Let X'OX and YOY' be the coordinate axes.



(i) On the x−axis, take 4 units to the right of the y axis; and then on the y−axis, take 3 units above the x−axis. Thus, we obtain the point A(4,3)


(ii) On the x−axis, take 2 units to the right of the y−axis; and then on the y−axis, take 6 units above the x−axis. Thus, we obtain the point B(2,6)


(iii) On the x−axis, take 3 units to the left of the y−axis; and then on the y−axis, take 5 units above the x−axis. Thus, we obtain the point C(−3,5)


(iv) On the x−axis, take 5 units to the left of the y−axis; and then on the y−axis, take 2 units above the x−axis. Thus, we obtain the point D(−5,2)


(v) On the x−axis, take 2 units to the left of the y−axis; and then on the y−axis, take 3 units below the x−axis. Thus, we obtain the point E(−2,−3)


(vi) On the x−axis, take 5 units to the left of the y−axis; and then on the y−axis, take 3 units below the x−axis. Thus, we obtain the point F(−5,−3)


(vii) On the x−axis, take 5 units to the right of the y−axis; and then on the y−axis, take 4 units below the x−axis. Thus, we obtain the point G(5,−4)


(viii) On the x−axis, take 3 units to the right of the y−axis; and then on the y−axis, take 3 units below the x−axis. Thus, we obtain the point H(3,−3)




Exercise 25b
Question 1.

Draw the graph of the function y = 3x.


Answer:

The given function is y=3x. For some different values of x, the corresponding values of y are given below:


Now, let us plot the points O(0,0), A(1,3) and B(2,6).



∴ Now, we obtain our required graph.



Question 2.

From the graph, find the value of y, when

(i) (ii) (iii)


Answer:

(i) Our point C to be plotted lies on function y = 3x.

Here, first plotting y = 3x.


Here, x = 3.


∴ Now for abscissa equal to 3, we plot the point on y = 3x, ie y = 3 × 3 = 9


Hence, the value of y is 9


(ii) Our point to be plotted lies on function y = 3x.


Here, first plotting y = 3x.


Here, x = 5.


∴ Now for abscissa equal to 5, we plot the point on y = 3x, ie y = 3 × 5 = 15


Hence, the value of y is 15


(iii) Our point to be plotted lies on function y = 3x.


∴Here, first plotting y = 3x.


Here, x = 6.


∴ Now for abscissa equal to 6, we plot the point on y = 3x, ie y = 3 × 6 = 18


Hence, the value of y is 18



Question 3.

Draw the graph of the function P = 4x.


Answer:

The given function is P = 4x. For some different values of x, the corresponding values of P are given below:


Now let us plot the points, O(0,0), A(1,4) and B(2,8)



∴ Now, we obtain our required graph.



Question 4.

From the graph, find the value of P, when

(i) (ii) (iii)


Answer:

(i) Our point C to be plotted lies on function P = 4x.

∴Here, first plotting P = 4x.


Here, x = 3.


∴ Now for abscissa equal to 3, we plot the point on P = 4x, ie P = 4 × 3 = 12


Hence, the value of P is 12


(ii) Our point D to be plotted lies on function P = 4x.


∴Here, first plotting P = 4x.


Here, x = 4.


∴ Now for abscissa equal to 4, we plot the point on P = 4x, ie P = 4 × 4 = 16


Hence, the value of P is 16


(iii) Our point E to be plotted lies on function P = 4x.


∴Here, first plotting P = 4x.


Here, x = 6.


∴ Now for abscissa equal to 6, we plot the point on P = 4x, ie P = 4 × 6 = 24


Hence, the value of P is 24



Question 5.

Draw the graph of the function A = x2.


Answer:

The given function is A=x2 .


For some different values of x, the corresponding values of A are given below:




Now let us plot the points, O(0,0), S(1,1) and P(2,4).



∴ Now we obtain the required graph.



Question 6.

From the graph, find the value of A, When

(i) (ii) (iii)


Answer:

(i) Our point B to be plotted lies on function A = x2.

∴Here, first plotting A = x2.


Here, x = 2.


∴ Now for abscissa equal to 2, we plot the point on A = x2., ie A = 22 = 4


Hence, the value of A is 4


(ii) Our point C to be plotted lies on function A = x2.


∴Here, first plotting A = x2.


Here, x = 3.


∴ Now for abscissa equal to 3, we plot the point on A = x2., ie A = 32 = 9


Hence, the value of A is 9


(iii) Our point to be plotted lies on function A = x2.


∴Here, first plotting A = x2.


Here, x = 4.


∴ Now for abscissa equal to 4, we plot the point on A = x2., ie A = 42 = 16


Hence, the value of A is 16




Exercise 25c
Question 1.

In which of the following quadrants does the point lie?
A. I

B. II

C. III

D. IV


Answer:

Here, given point is P(3,6).


Both the coordinates are positive.


Hence, point P lies in first quadrant.


Question 2.

In which of the following quadrants does the point lie?
A. I

B. II

C. III

D. IV


Answer:

Here, given point is (-7,-1).


Both the coordinates are negative.


Hence, given point lies in third quadrant.


Question 3.

In which of the following quadrants does the point lie?
A. I

B. II

C. III

D. IV


Answer:

Here, given point is .


Here, abscissa of a point is positive and ordinate is negative.


Hence, given point lies in fourth quadrant.


Question 4.

In which of the following quadrants does the point lie?
A. I

B. II

C. III

D. IV


Answer:

Here, given point is


Here, abscissa of a point is negative and ordinate is positive.


Hence, given point lies in second quadrant.


Question 5.

The abscissa of a point is its distance from the
A. origin

B. x-axis

C. y-axis

D. none of these


Answer:

We know that the abscissa of a point is its distance from the y−axis.


Question 6.

The graph of y = a is
A. the x-axis

B. the y-axis

C. a line parallel to the y-axis

D. a line parallel to the x-axis


Answer:

Here, the line y = a is parallel x-axis.


Question 7.

The equation representing the y-axis is
A.

B.

C.

D.


Answer:

We know that the graph x = a is a line parallel to the y-axis.


Hence, for x = 0, line represents y axis.