So 7 friends with similar. Phone plans. 3 of them pays an extra 4 bucks, so that means that x+ 4 is what 3 of the 7 r paying. The other 4 pay just x Amt of money for their plan. So go find the total bill, it would be (x+4)+(x+4)+(x+4)+x+x+x+x. Now simplify, (x+4)^3, because there are three of the 7 using that, and then x^4, because 4 of the 7 r using that plan. So in total it would be (x+4)^3+ x^4. Hope this helps
Answer:
The speed on motorboat is 20 mph
Step-by-step explanation:
here, we want to find the speed on the motorboat
if he has a speed of x mph on the motor boat, his speed on the ski will be (x + 10) mph
The total hours is 4 hours
Mathematically; speed = distance/time
Time on ski is 27/x+ 10
Time on motor boat is 62/x
The addition of both is 4
Thus;
27/(x + 10) + 62/x = 4
27(x) + 62(x + 10) = 4(x)(x + 10)
27x + 62x + 620 = 4(x^2 + 10x)
89x + 620 = 4x^2 + 40x
4x^2 -49x-620 = 0
using the quadratic formula;
{-b ± √(b^2-4ac)}/2a
where a = 4, b = -49 and c = -620
= 49 ± √(-49)^2-4(4)(-620)/8
So we have
49+ 111/8 or 49-111/8
Speed cannot be negative
(49 + 111)/8
= 20 mph
the answer is 10! because 7*10= 70
