Explanation:
f(3)=?
f(x)=2x+5
put x=3,
f(3)=2(3)+5=6+5=11
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g(2)=?
g(x)=x^2-3
put x=2,
g(2)=2^2-3=4-3=1
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g(f(-1))=?
g(x)=x^2-3
and f(-1)=2(-1)+5= -2+5=3
so g(f(-1))=3^2-3=9-3=6
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f(g(-1))=?
f(x)=2x+5
g(x)=g(-1)=(-1)^2-3=1-3= -2
f(g(-1))=2(-2)+5= -4+5=1
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g(f(x))=?
g(x)= x^2-3
put x=f(x),
g(f(x))=f(x)^2-3=(2x+5)^2-3=4x+25+20x-3=24x+25