a. Let f(x1)=f(x2). It means that
2x1+3=2x2+32x1=2x2x1=x2The function f(x)=2x+3 is one-to-one from R to R.
Let y=2x+3,y∈R. Then
x=2y−23We see that x∈R ∀y∈R.
The function f(x)=2x+3 is onto from R to R.
b. Let g(x1)=g(x2). It means that
−3x2+5=−3x2+5−3x1=−3x2x1=x2The function g(x)=−3x+5 is one-to-one from R to R.
Let y=−3x+5,y∈R. Then
x=−3y+35We see that x∈R ∀y∈R.
The function g(x)=−3x+5 is onto from R to R.
c.
g∘f=−3(2x+3)+5=−6x−4g∘f=−6x−4
d.
f(x)=2x+3,x∈Ry=2x+3Change x and y
x=2y+3Solve for y
y=21x−23Then
f−1(x)=21x−23
g(x)=−3x+5,x∈Ry=−3x+5Change x and y
x=−3y+5Solve for y
y=−31x+35Then
g−1(x)=−31x+35
e.
g∘f=−6x−4y=−6x−4Change x and y
x=−6y−4Solve for y
y=−61x−32Then
(g∘f)−1(x)=−61x−32
f−1∘g−1=21(−31x+35)−23=−61x−32
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