First divide by 3 because we don't want any factor in front of the x² when doing factorization:
3x² + 15x – 18 = 0 => x² + 5 - 6 = 0
Then find the two numbers that multiply to -6 and add up to +5:
x² + 5 - 6 = 0 => (x-1)(x+6) = 0
So the solutions are x=1 or x=-6, that's answer B.
Answer:
The time it will take is 8hours 45mins.
Step-by-step explanation:
Since y = –240x represents a submarine descent. We are looking for how long, that is the time, it will take for the submarine to make a descent of 2100. We know that y is the elevation, if it is descending it will be in the negative direction, making it -ve.
A descent of 2100 means y = –2100. Hence,
–2100 = –240x
x = –2100/–240 = 8.75hours = 8hours 45minutes. (0.75hours = 3/4hours = 3/4 x 60mins = 45mins).
