if a + b + c = 9 and a square + b square + c square = 35 the find the value of ab + bc + ca .​ I am in need of help

Bugs bunny was 33 meters below ground, digging his way toward pismo beach, when he realized he wanted to be above ground. he turned and dug through the dirt diagonally for 80 meters until he was above ground

Researchers were interested in whether relaxation training decreases the number of headaches a person experiences. they randomly assigned 20 participants to a control group or a relaxation training group and noted the change in number of headaches each group reported from the week before training to the week after training. which statistical analysis should be performed to answer the researchers' question?

A. 127 cm^2 b. 144.5 cm^2 c. 172 cm^2 d. 50 cm^2