solve
7^(x+2) - 2.7^(-x) + 97 = 0
Printable View
solve
7^(x+2) - 2.7^(-x) + 97 = 0
7^(x+2) - 2.7^(-x) + 97 = 0
is the same as
7^(x+2) - (1/(2.7^(x)) + 97 = 0
That should get you started!
72.7x - 2.7-x + 97 = 0Quote:
Originally Posted by fiery123
49.7x - 2.7-x + 97 = 0
Multiply through by 7x
49.(7x)2 - 2 + 97.7x = 0
49.(7x)2 + 97.7x - 2 = 0
This is a quadratic so solve the quadratic first
(49.7x - 1)(7x + 2) = 0
7x = 1/49 or 7x = -2
x = -2 or No possible solutions
So x = -2
I think you made a mistake
In the second line you have 49.7 which was 49 *7, so you use the "." as a multiplier. But in the term 2.7 the "." is a decimal.
In the third line you have used both "." as a multiplier, that way you could come up with the -2!
i actually made the mistake. At first when i read the question i thought that the "." was a decimal. But when i look closely again the "." was actually a multiplication sign, since it was kind of in the middle. And -2 is right anyway from the answers. So thanks.
And i'll look more carefully at the question before posting next time.
It is usual in these questions to use . as a multiplier. The question would be very difficult if it was 2.7 and it is hard to believe it would have such an elegant solution as it does as 2 * 7Quote:
Originally Posted by opus
If all solutions would be easy and elegant, my grades in school would have been much better.
But that's a story from the last century.