What reason could be used to prove that a parallelogram is a rhombus?

Which of the following vectors are orthogonal to (2,1)? check all that apply

Thirteen bowlers were asked what their score was on their last game. the scores are shown below 190,150,154,194,181,190,170,151,170,178,161,180 find the range of the bowlers score a.56 b.44 c.34 d.23

What is the expression equivalent to (3x^2-7)