Answer: solutions are the same, just written differently, inequality sign is reversed when multiplying by a negative. Yes, both students are correct.Jul 8, 2018
Step-by-step explanation:
We will use demonstration of recurrences<span>1) for n=1, 10= 5*1(1+1)=5*2=10, it is just
2) assume that the equation </span>10 + 30 + 60 + ... + 10n = 5n(n + 1) is true, <span>for all positive integers n>=1
</span>3) let's show that the equation<span> is also true for n+1, n>=1
</span><span>10 + 30 + 60 + ... + 10(n+1) = 5(n+1)(n + 2)
</span>let be N=n+1, N is integer because of n+1, so we have
<span>10 + 30 + 60 + ... + 10N = 5N(N+1), it is true according 2)
</span>so the equation<span> is also true for n+1,
</span>finally, 10 + 30 + 60 + ... + 10n = 5n(n + 1) is always true for all positive integers n.
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</span>
Answer:
98 ft²
Step-by-step explanation:
There are a couple of ways you can think about this one. Perhaps easiest is to treat it as a square with a triangle cut out of it. The cutout triangle has a base (across the top) of 14 ft and a height of 14 ft, so its area is ...
A = (1/2)(14 ft)(14 ft) = 98 ft²
Of course the area of the square from which it is cut is ...
A = (14 ft)² = 196 ft²
So, the net area of the two triangles shown is ...
A = (196 ft²) - (98 ft²) = 98 ft²
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Another way to work this problem is to attack it directly. Let the base of the left triangle be x. Then the base of the right triangle is 14-x, and their total area is ...
A = A1 + A2 = (1/2)(x ft)(14 ft) + (1/2)((14-x) ft)(14 ft)
We can factor out 7 ft to get ...
A = (7 ft)(x ft + (14 -x) ft)
A = (7 ft)(14 ft) = 98 ft²
Answer:
-2n^2 - 12n, that's how I understand
