2x^2+20x=-38 divide both sides by 2
x^2+10x=-19, halve the linear coefficient, square it, than add that value to both sides of the equation, in this case add (10/2)^2=25...
x^2+10x+25=6 now the left side is a perfect square
(x+5)^2=6 take the square root of both sides
x+5=±√6 subtract 5 from both sides
x=-5±√6 (so answer c.)
Your answer should be 12,500,000
Remember that c is the initial height. Since we the rocket is in a 99-foot cliff, c=99. Also, we know that the velocity of the rocket is 122 ft/s; therefore v=122
Lets replace the values into the the vertical motion formula to get:
Notice that the rocket hits the ground at the bottom of the cliff, which means that the final height is 99-foot bellow its original position; therefore, our final height will be h=-99
Lets replace this into our equation to get:
Now we can apply the quadratic formula
where a=-16, b=122, and c=198
or
or
or
Since the time can't be negative, we can conclude that the rocket hits the ground after 9 seconds.
Multiply 17x5=85,85+5=90 so aswer is 90