Y=2x
x+y=9
solve using substitution

Multiplying an even number of negative numbers gives an answer that is choose from:

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

Which shows the correct substitution of the values a,b and c from the equation 1=-2x+3x^2+1