prove by mathematical induction 1cube+2cube+3cube+.......+ncube=nsquare(n+1)square/4
Answers
Step-by-step explanation:
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The statement that 1³+2³ +3³ +.......+n³ =n²(n+1)²/4 is proved by the Principle of Mathematical Induction.
Given
1³+2³ +3³ +.......+n³ = n²(n+1)²/4
To Find
Proof of the statement 1³+2³ +3³ +.......+n³ = n²(n+1)²/4 by Principle of Mathematical Induction
Solution
Statement- 1³+2³ +3³ +.......+n³ = n²(n+1)²/4
Step 1, n = 1
LHS
1³ = 1
RHS
1² X (1 + 1)²/4
= 1 X 2²/4
4/4
= 1
Therefore, the statement is true for n = 1
Step 2, n = k
Let us assume that the statement holds true for n = k
Hence,
1³ + 2³ + .... + k³ = k²(k+ 1)²/4 [1]
Step 3, n = k + 1
LHS
= 1³ + 2³ + 3³ + ... + k³ + (k + 1)³
= k²(k+ 1)²/4 + (k + 1)³ [from equation [1]]
Taking (k+ 1)² common we get
(k+ 1)²[k²/4 + k + 1]
= (k+ 1)²[(k²+ 4k + 4)/4 ]
= (k+ 1)²[(k²+ 2.2.k + 2²)/4 ]
= (k + 1)²(k + 2)²/4
RHS
(k + 1)²(k + 1 + 1)²/4
= (k + 1)²(k + 2)²/4
Hence LHS = RHS,
The statement that 1³+2³ +3³ +.......+n³ =n²(n+1)²/4 is proved by the Principle of Mathematical Induction.
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