Please help solve for x and y

Describe the 2 algebraic methods you can use to find the zeros of the function f(t)=-16t^2+400.

The figure shows triangle def and line segment bc, which is parallel to ef: triangle def has a point b on side de and point c on side df. the line bc is parallel to the line ef. part a: is triangle def similar to triangle dbc? explain using what you know about triangle similarity. part b: which line segment on triangle dbc corresponds to line segment ef? explain your answer. part c: which angle on triangle dbc corresponds to angle f? explain your answer. asap

Which two fractions are equivalent to 24/84? 6/42 and 2/7 6/21 and 2/6 12/42 and 3/7 12/42 and 2/7