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Tamil Nadu Board of Secondary EducationSSLC (English Medium) Class 8

Revision: Algebra Mathematics SSLC (English Medium) Class 8 Tamil Nadu Board of Secondary Education

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Definitions [7]

Definition: Unlike Terms

The terms that do not have the same literal coefficients are called unlike terms. 

For example:

6a, 6ab and 6ac are unlike terms. 

Definition: Like Terms

Terms having the same literal part (same variables with the same powers) are called like terms.

For example:

xy, 5xy, -4xy, etc. are like terms 

Identity: An identity is an equality, which is true for all values of the variables in equality.

A balanced equation is one in which the value of the left-hand side (LHS) is equal to the value of the right-hand side (RHS).

A Pictograph is a chart that uses pictures or symbols to represent data. Each picture stands for a specific number of items, making the data easy to understand at a glance.

Definition: Co-ordinate Axes

The two mutually perpendicular number lines intersecting each other at their zeroes are called rectangular axes or coordinate axes, or axes of reference. 

Definition: Co-ordinates

The position of a point in a plane is expressed by a pair of numbers, one concerning the x-axis and the other concerning the y-axis. called co-ordinates. 

  • x → distance from y-axis (abscissa)

  • y → distance from x-axis (ordinate)

Formulae [7]

(a + b)2 = a2 + 2ab + b2

(a - b)2 = a2 - 2ab + b2.

(a + b)(a - b) = a2 - b2

  • (x + a)(x + b) = x2 + (a + b)x + ab
  • (a + b)3 = a3 + 3a2b + 3ab2 + b3.
  • (a - b)3 = a3 - 3a2b + 3ab2 - b3.
  • (a + b)2 = a2 + 2ab + b2
  • (a - b)2 = a2 - 2ab + b2
  • (a + b)(a - b) = a2 - b2

Key Points

Key Points: Co-ordinate Geometry

Sign Convention

  • Right of y-axis → +x

  • Left of y-axis → −x

  • Above x-axis → +y

  • Below x-axis → −y

Standard Line Results

  • x = 0 → y-axis

  • y = 0 → x-axis

  • x = a → line parallel to the y-axis

  • y = b → line parallel to the x-axis

Quadrant Reminder

Quadrant Sign of (x, y)
I (+, +)
II (−, +)
III (−, −)
IV (+, −)
Key Points: Graphical Method
Condition Nature of Lines Number of Solutions Type of Pair
\[\frac{a_1}{a_2}\neq\frac{b_1}{b_2}\] Intersecting One (unique) solution Consistent
\[\frac{a_1}{a_2}=\frac{b_1}{b_2}\neq\frac{c_1}{c_2}\] Parallel No solution Inconsistent
\[\frac{a_1}{a_2}=\frac{b_1}{b_2}=\frac{c_1}{c_2}\] Coincident Infinitely many solutions Dependent (consistent)

Concepts [43]

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