Which value must be added to the expression x^2+12x to make it a perfect square tinomial

Idont get this question can someone me solve it? ** the distance light travels in one second (1 light second) is about 1.86 ×10^5 mi. saturn is about 475 light-seconds from the sun. about how many miles from the sun is saturn..my guess is 8.83* 10^7 you so much

Select the lengths in centimeters that would form a right triangle

Evaluate cos2θ for cosθ = square root of 3/2