X=5
7(5)-8=35-8=27
3(5)+12=15+12=27
Recall that A = 1/2bh.
We are given that h = 4+2b
So, putting it all together:
168 = 1/2 b(4+2b)
168 = 1/2(4b + 2b^2)
168 = 2b + b^2
b^2 + 2b - 168 = 0.
Something that multiplies to -168 and adds to 2? There's a trick to this.
Notice 13^2 = 169. So, it's more than likely in the middle of the two numbers we're trying to find. So let's try 12 and 14. Yep. 12 x 14 = 168. So this factors into (b+14)(b-12) So b = -14 or b =12. Is it possible to have a negative length on a base? No. So 12 must be our answer.
Let's check this. If 12 is our base, then according to our problem, 2*12 + 4 would be our height... or 28. so what is 12 * 28 /2?
196. Check.
Hope this helped!
To determine the minimum of an equation, we derive the <span>equation using differential calculus twice (or simply </span><span>take the second derivative of the function). If the </span><span>second derivative is greater than 0, then it is minimum; </span><span>else, if it is less than 1, the function contains the </span><span>maximum. If the second derivative is zero, then the </span><span>inflection point </span><span>is</span><span> identified.</span>
Area = πr^2
π4^2 =16π
=50.3
