(b) Find the number of terms in an arithmetic series which has its first term 7, common difference 4 and the sum 900.

blue stars have the highest surface temp

stellar distances are usually expressed in light-years

the measure of a star's brightness is called magnitude

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the menstrual cycle – higher tier. negative feedback mechanisms affect the production of hormones in the menstrual cycle. oestrogen also stimulates the release of lh (luteinising hormone) from the pituitary gland, which in turn controls the production of progesterone.

answer; the tunica intima also called tunica interna, consists of elastic fibers,connective tissue and smooth muscle cells;