I got the answer of 21.5, but it doesn't have it in your option list :(
Take the deritive
y'=-3sinx
find whre it equals 0
it equals 0 at -pi, 0, pi, etc
find whre it changes from negative to positive
at -0.5pi, the derivitive is positive
at 0.5pi, the deritivie is negative
changes from positive to negative at x=0
that means that the max values are at pi and -pi in 2pi intervals
-pi, pi, 3pi, 5pi,etc
the min y value is -3
so the minimum(s) are/is at (2aπ,-3) where 'a' is an integer
(a) Without solving the equation we can't determine whether its true or false.
(b) If x = 3
4x + 1 = 2x + 5
4(3) + 1 = 2(3) + 5
12 + 1 = 15 + 5
13 = 20
No, if x = 3, the equation will not be true.
(c) 4x + 1 = 2x + 5
4x - 2x = 5 - 1
2x = 4
x = 4/2
x = 2
This shows that x = 2 makes the equation true.
Mathematical equation -
20 + 0.50x = ?
X is the placeholder which in this case equals months
But in this case you want to look for form month three to month 18 (which is 15 months) so three months went by so the equation is
$61.50(being the three months already)
(20+(0.50*15))+61.50=?
