pls someone solve these problems
1. show that f:R-R defined by f(x) = 2x3 -7 for all x belonging to R is bijective
2. f(x) = x+7 g(x) = x-7 x belonging to R find (fog)(7)
3.f(x) = x3 g(x)= cos3x find fog(x)
4.f:R-R f(x) = x/x2 +1 find f (f (x))
5. f:R-R f(x) = x2 - 3x + 2 find f (f (x))
6.f(x) = mode x g(x) = [x] f:R-R find fog(5/ 2) gof ( - square root 2) where [ greatest integer function]
2.) fx = x+7 ......(1)
gx = x-7
fog(x) = (x-7) +7 { by substituting x by g(x) in (1) }
fog(x) = x
=>fog(7) = 7.