Answer:
its B , 4 11/20
Step-by-step explanation:
2cos²x+cos x-1=0
cos x=t
2t²+t-1=0
t=[-1⁺₋√(-1+8)]/2=(-1⁺₋3)/4
We have two possible set solutions:
First set solutions.
t₁=(-1-3)/2=-4/4=-1
cos x=-1 ⇒x=cos⁻¹ (-1)=π +2kπ or 180º+360ºk (k=(...-2,-1,0,1,2...)
Second set solutions:
t₂=(-1+3)/4=2/4=1/2
cos x=1/2 ⇒ x=cos⁻¹ 1/2=π/3+2kπ U 5π/3+ 2kπ or
60º+360ºK U 300º+360ºK (k=...-2,-1,0,1,2,...)
solutions: first set solutions U second set solutions:
Answer in radians : π +2kπ U π/3+2kπ U 5π/3+ 2kπ (k=...-1,0,1,...)
Answer is degrees: 180º+360ºk U 60º+360ºK U 300º+360ºK (k=...-2,-1,0,1,2,...)
2(x + 5) = 40 ....................
Answer:
66
Step-by-step explanation:
105+420=525 (Total Money)
7x3.25=22.75 (Cost of all bracelets)
8x11.74=93.92 (Cost of all necklaces)
93.92+22.75=116.67 (Cost of all Christmas presents)
525-116.67=408.33 (Total money - Cost of all Christmas presents)
408.33/6.15=66.39... (Amount of necklaces)
since in real life you can only buy a whole number of things, you would round down 66.39 to 66. I hope this helped!
