12 multiple-choice questions, progressively harder.
The rule y=f(2x−6)y = f(2x - 6)y=f(2x−6) transforms y=f(x)y = f(x)y=f(x). Factoring the input, which describes it?
Solution
Correct answer: B
Factor the inside into the form b(x−h)b(x - h)b(x−h) before reading the moves.
2x−6=2(x−3)2x - 6 = 2(x - 3)2x−6=2(x−3)
So b=2b = 2b=2 (a horizontal compression by 222) and h=3h = 3h=3 (right 333). Reading −6-6−6 without factoring gives the wrong 'right 666.'
The rule y=f(3x+12)y = f(3x + 12)y=f(3x+12) transforms y=f(x)y = f(x)y=f(x). Factoring the input, which describes it?
Correct answer: D
Factor the inside into the form b(x−h)b(x - h)b(x−h).
3x+12=3(x+4)=3(x−(−4))3x + 12 = 3(x + 4) = 3\big(x - (-4)\big)3x+12=3(x+4)=3(x−(−4))
So b=3b = 3b=3 (a horizontal compression by 333) and h=−4h = -4h=−4 (left 444). Reading +12+12+12 without factoring gives the wrong 'left 121212.'
The graphs y=2f(x)+3y = 2f(x) + 3y=2f(x)+3 and y=2(f(x)+3)y = 2(f(x) + 3)y=2(f(x)+3) differ. By what constant vertical amount is the second above the first?
Correct answer: A
Expand the second rule and subtract the first.
2(f(x)+3)−(2f(x)+3)=(2f(x)+6)−(2f(x)+3)=32(f(x) + 3) - (2f(x) + 3) = (2f(x) + 6) - (2f(x) + 3) = 32(f(x)+3)−(2f(x)+3)=(2f(x)+6)−(2f(x)+3)=3
The second is 333 higher everywhere, because the stretch also multiplied the 333.
For f(x)=x2+4f(x) = x^2 + 4f(x)=x2+4, does the compression y=f(3x)y = f(3x)y=f(3x) equal a vertical stretch c f(x)c\,f(x)cf(x)?
Compute both and try to match.
f(3x)=9x2+4,c f(x)=cx2+4cf(3x) = 9x^2 + 4, \qquad c\,f(x) = c x^2 + 4cf(3x)=9x2+4,cf(x)=cx2+4c
The x2x^2x2 term needs c=9c = 9c=9 but the constant needs 4c=44c = 44c=4, that is c=1c = 1c=1, so no single ccc works.
'Stretch vertically by 222, then shift up 333' gives which rule from y=f(x)y = f(x)y=f(x)?
Apply the moves in order to the output, stretch first and then shift.
f(x) → 2f(x) → 2f(x)+3f(x) \ \to\ 2f(x) \ \to\ 2f(x) + 3f(x) → 2f(x) → 2f(x)+3
The stretch happens before the shift, so the 333 is not multiplied.
A function ggg is odd on a domain symmetric about 000, and (4,7)(4, 7)(4,7) is on its graph. Which point must also be on the graph?
Odd means negating the input negates the output.
g(−4)=−g(4)=−7g(-4) = -g(4) = -7g(−4)=−g(4)=−7
So (−4,−7)(-4, -7)(−4,−7) is on the graph, a 180∘180^\circ180∘ rotation of (4,7)(4, 7)(4,7) about the origin.
The point (u,v)(u, v)(u,v) lies on y=f(x)y = f(x)y=f(x). Under y=af(b(x−h))+ky = a f(b(x - h)) + ky=af(b(x−h))+k with b≠0b \ne 0b=0, where does it land?
Correct answer: C
Solve the inside b(x−h)=ub(x - h) = ub(x−h)=u for xxx, and read the output off the outside.
x=ub+h,y=av+kx = \tfrac{u}{b} + h, \qquad y = a v + kx=bu+h,y=av+k
The input is divided by bbb then shifted by hhh; the output is scaled by aaa then shifted by kkk.
The point (p,q)(p, q)(p,q) is on y=f(x)y = f(x)y=f(x). Under y=af(b(x−h))+ky = a f(b(x - h)) + ky=af(b(x−h))+k, where does it land?
Solve the inside b(x−h)=pb(x - h) = pb(x−h)=p for xxx, and read the output off the outside.
x=pb+h,y=aq+kx = \tfrac{p}{b} + h, \qquad y = a q + kx=bp+h,y=aq+k
Is f(x)=x3f(x) = x^3f(x)=x3 even, odd, or neither, and what invariance does that give its graph?
Test the parity by substituting −x-x−x.
f(−x)=(−x)3=−x3=−f(x)f(-x) = (-x)^3 = -x^3 = -f(x)f(−x)=(−x)3=−x3=−f(x)
So fff is odd, and oddness is invariance under a 180∘180^\circ180∘ rotation about the origin.
Reflect y=f(x)y = f(x)y=f(x) across the xxx-axis, then shift up 222. The point (5,4)(5, 4)(5,4) on fff lands where?
Negate the height, then add 222; the input stays.
(5,4) → (5,−4) → (5, −4+2)=(5,−2)(5, 4) \ \to\ (5, -4) \ \to\ (5,\ -4 + 2) = (5, -2)(5,4) → (5,−4) → (5, −4+2)=(5,−2)
Reflect first, so +2+2+2 acts on the negated height.
With f(x)=x2f(x) = x^2f(x)=x2, which statement about transforming y=f(x)y = f(x)y=f(x) into y=4x2y = 4x^2y=4x2 is TRUE?
Both a horizontal and a vertical move reach the same graph.
f(2x)=4x2=4f(x)f(2x) = 4x^2 = 4f(x)f(2x)=4x2=4f(x)
So the transformation is not unique: it can be a compression by 222 or a stretch by 444, and the finished graph cannot tell you which was applied.
The point (−2,5)(-2, 5)(−2,5) is on y=f(x)y = f(x)y=f(x). Which point must lie on y=f(−x)y = f(-x)y=f(−x)?
Negating the input reflects across the yyy-axis, flipping the input's sign while the height stays.
(2, 5)(2,\ 5)(2, 5)
The height 555 is unchanged; the input −2-2−2 becomes 222.
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