Shortcut Trick
Substitute a = 2 and b = 5 directly into the expression.
(a + b)5 = 75 = 16807 and (a − b)3 = (−3)3 = −27.
Numerator = 16807 − (−27) = 16807 + 27 = 16834.
Denominator = 4 × 2 × 5 = 40.
Expression = 16834 ÷ 40 = 420.85.
∴ The correct answer is 420.85.
Alternate Method
Given:
Variable a = 2
Variable b = 5
Expression to evaluate: [(a + b)5 − (a − b)3] ÷ (4ab)
Step-by-step Calculation:
⇒ First, find the values of (a + b) and (a − b):
⇒ (a + b) = 2 + 5 = 7
⇒ (a − b) = 2 − 5 = −3
⇒ Calculate the powers:
⇒ (7)5 = 7 × 7 × 7 × 7 × 7 = 16807
⇒ (−3)3 = (−3) × (−3) × (−3) = −27
⇒ Substitute these into the numerator:
⇒ Numerator = 16807 − (−27) = 16807 + 27 = 16834
⇒ Calculate the denominator:
⇒ 4ab = 4 × 2 × 5 = 40
⇒ Divide the numerator by the denominator:
⇒ Result = 16834 ÷ 40 = 420.85
∴ The correct answer is 420.85.
Additional Information
BODMAS Rule
This rule dictates the order of operations: Brackets, Of, Division, Multiplication, Addition, and Subtraction.
Negative Base Exponents
A negative base raised to an odd power remains negative, e.g., (−x)3 = −x3, while an even power makes it positive, e.g., (−x)2 = x2.
Powers of 7
Knowing common powers like 72 = 49, 73 = 343, 74 = 2401, and 75 = 16807 helps in quick simplification.