Solution
For graphing:
- Use a small table of convenient x values.
- Note transformations (shifts, reflections, stretches).
- State the domain restriction if a square root is involved.
(i) y=3x
Domain: 3x≥0⇒x≥0.
Choose 3x as perfect squares: 3x=0,1,4,9,16.
xy=3x00311342333164
Domain [0,∞),Range [0,∞)
(ii) y=x+5
Domain: x≥0.
xy=x+505164798169
This is y=x shifted up by 5.
Domain [0,∞),Range [5,∞)
(iii) y=−21x
Domain: x≥0.
xy=−21x001−214−19−2316−2
Reflection in x-axis and vertical shrink by factor 21.
Domain [0,∞),Range (−∞,0]
(iv) y=−x+1+2
Domain: x+1≥0⇒x≥−1.
Choose x+1=0,1,4,9,16.
xy=−x+1+2−1201308−115−2
This is y=x shifted left by 1, reflected, then shifted up by 2.
Domain [−1,∞),Range (−∞,2]
(v) y=32x+1
Cube root is defined for all real numbers.
Pick 2x+1=−8,−1,0,1,8.
2x+1xy=32x+1−8−29−2−1−1−10−2101018272
Domain R,Range R
(vi) y=23x−3
Pick x=−8,−1,0,1,8.
x3xy=23x−3−8−2−7−1−1−500−311−1821
Stretch by 2 and shift down by 3.
Domain R,Range R
(vii) y=3x2+x−2
Cube root is defined for all real numbers, so domain is all real numbers.
Compute a few points:
xx2+x−2y=3x2+x−2−200−1−2−320−2−321002434
Domain R