NCERT Class 9 Solution: Linear Equation In Two Variables (Chapter 4) Exercise 4.1

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Line ax+by+c = 0 on the coordinate plane

Equaltion of a Line Plotted on the Coordinate Plane

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Q-1 The cost of a notebook is twice the cost of a pen. Write a linear equation in two variable to represent this statement.

(Take the cost of a notebook to be Rs and that of a pen to be Rs )

Solution:

Consider the cost of a notebook be and that of a pen be .

A linear equation has to equate the two things. According to question, the cost of a notebook is twice the cost of a pen

So,

Therefore, linear equation becomes,

.

Q-2 Express the following linear equations in the form and indicate the value of in each case:

i.

ii.

iii.

iv.

v.

vi.

vii.

viii.

Solution:

i.

  • So,

  • Compare, the equation with

  • Therefore, value of and is

ii.

  • Compare the equation with .

  • Therefore, .

iii.

  • So,

  • Compare, the equation with

  • Therefore,

iv.

  • So,

  • Compare, the equation with

  • Therefore,

v.

  • So,

  • Compare, the equation with

  • Therefore,

vi.

  • Compare, the equation with

  • Therefore,

vii.

  • Compare, the equation with

  • Therefore,

viii.

  • So,

  • Compare, the equation of

  • Therefore,