MATHS PREPARATION FOR WAEC 2018 EXAM BY EXPOROOM

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Maths Preparation for 2018 Waec
#Equation/#Identity- what’s the difference?
Many students often used equation and identity,but they don’t know the difference between them and what notation do we use. Well, this post will aim to explain the difference.
An equation contains ( = )
An identity contains ( ≡ )
Where,
( = ) means “equal to”
( ≡ ) means “can be written as”
#IDENTITY
Supposed you were asked to find x below.
2(x+3) = 5x-3(x-2)
Expanding the brackets gives:
2x+6 = 5x-3x+6
Combine like terms on the RHS :
2x+6 = 2x+6
Subtract 2x from both sides :
6 = 6
This may sounds confusing, getting the same number value on each side when you are asked to find x. This shows that the LHS is exactly the same as the RHS. They are identical. Therefore,the expression above should be written as :
2(x+3) ≡ 5x-3(x-2)
It’s an identity!
An identity is true for any value.For example,let’s plug in 2 into the identity.
That’s ,when x = 2 :
2(2+3)≡5(2)-3(2-2)
∴ 10 ≡ 10
Let’s also try when x = 3 :
2(3+3)≡5(3)-3(3-2)
∴ 12 ≡ 15 – 3
∴ 12 ≡ 12
It will be true for all values.
#EQUATION
Let’s find x in the equations below :
(1). 5x + 5 = 4x + 7
Collecting like terms,gives :
x = 2
(2). Solve for x :
x² = 16
Applying square root on both sides,gives :
∴ x = ± √16
∴ x = ±4
You noticed that x is alone in each cases above.They are equations.An equation is true for one or two values but not for all values.
As in the illustrations above, the equation is only true when x=2 in equation (1) and true for when x = ±4 in equation (2).
When to use identity( ≡ )or equation ( = ) ?
#IDENTITY
Use identity ( ≡ ) when you are asked to :
#Expand
That’s,
(x-2)(x+3) ≡ x² + x – 6
#Factorize
that’s,
x² – 9 ≡ (x+3)(x-3)
#Simplify
that’s ,
2x-5+x = 3x – 5
EQUATION
Use equation ( =) when you are ask to solve. Example ,
Solve : x + 5 = 6
∴ x = 1

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