Jika $f(x)=\sqrt{x^2+2x-2}$ dan $g(x)=x^2+3$, maka $(g o f)(x)-g(x)-\sqrt{(g o f)(x)}=$ ...
A. $x$
B. $x-1$
C. $x-2$
D. $x-3$
E. $x-4$
Jawab; E
$(g o f)(x)-g(x)-\sqrt{(g o f)(x)}=g(f(x))-g(x)-\sqrt{g(f(x))}$
$ =g(\sqrt{x^2+2x-2}-[x^2+3]-[\sqrt{g(\sqrt{x^2+2x-2})}]$
$ =[\sqrt{x^2+2x-2}]^2-[x^2+3]-\sqrt{[\sqrt{x^2+2x-2}]^2+3}$
$ =x^2+2x-2-x^2-3-\sqrt{x^2+2x-2+3}$
$ =2x-3-\sqrt{x^2+2x-2+3}$
$ =2x-3-\sqrt{x^2+2x+1}$
$ =2x-3-\sqrt{(x+1)^2}$
$ =2x-3-(x+1)$
$ =2x-3-x-1$
$ =x-4$
Sumber Soal; Mandiri Matematika Jilid 1 untuk SMA/MA Kelas X Kelompok Wajib, Halaman 93 No. 86
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