Question in-the

1.3 Linear Equations in Two Variables - Writing equations from data/points
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In the linear function h h(0)=41 and h(1)=40. Which equation defines h ?

A.

h(x)=-x+41

B.

h(x)=-x

C.

h(x)=-41x

D.

h(x)=-41

In the linear function h , h ( 0 ) = 41 and h ( 1

Medium-difficulty · SAT Math · Linear Equations in Two Variables — Writing equations from data/points. Read the question above, select your answer, and check the full explanation below to understand exactly why the correct choice works.

Answer explanation

Choice A is correct. An equation defining a linear function can be written in the form hx=ax+b, where a and b are constants. It’s given that h0=41. Substituting 0 for x and 41 for hx in the equation hx=ax+b yields 41=a0+b, or b=41. Substituting 41 for b in the equation hx=ax+b yields hx=ax+41. It’s also given that h1=40. Substituting 1 for x and 40 for hx in the equation hx=ax+41 yields 40=a1+41, or 40=a+41. Subtracting 41 from the left- and right-hand sides of this equation yields -1=a. Substituting -1 for a in the equation hx=ax+41 yields hx=-1x+41, or hx=-x+41.

Choice B is incorrect. Substituting 0 for x and 41 for hx in this equation yields 41=-0, which isn't a true statement.

Choice C is incorrect. Substituting 0 for x and 41 for hx in this equation yields 41=-410, or 41=0, which isn't a true statement.

Choice D is incorrect. Substituting 41 for hx in this equation yields 41=-41, which isn't a true statement.