Determine the number of solutions for the system 6x+9y=9 and -6x+6y=1

Which sum or difference identity would you use to verify that cos (180° - ∅) = -cos ∅? a. sin (α -β) = sin α cos β – cos α sin β b. cos (α -β) = cos α cos β – sin α sin β c. cos (α -β) = cos α cos β + sin α sin β d. sin (α + β) = sin α cos β + cos α sin β

Identify a1 and r for the geometric sequence an= -256(-1/4) n-1

What two criteria are needed for triangles to be similar