How can you tell if radicals are like radicals?
1 answer:
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The sum of the first n odd numbers is n squared! So, the short answer is that the sum of the first 70 odd numbers is 70 squared, i.e. 4900.
Allow me to prove the result: odd numbers come in the form 2n-1, because 2n is always even, and the number immediately before an even number is always odd.
So, if we sum the first N odd numbers, we have
The first sum is the sum of all integers from 1 to N, which is N(N+1)/2. We want twice this sum, so we have
The second sum is simply the sum of N ones:
So, the final result is
which ends the proof.
Answer:
13 square units
Step-by-step explanation:
The bounding rectangle is 4 units wide and 5 units high, so has an area of 4×5 = 20 square units. From that are subtracted the areas of 4 triangles. 2 of them are 3 wide and 1 high, so have a combined area of 3×1 = 3 square units. The other two are 1 wide and 4 high, so have a combined area of 1×4 = 4 square units.
Then the area of the parallelogram is ...
20 -3 -4 = 13 . . . . square units
