Question which-

2.4 Equivalent Expressions - Simplifying polynomials
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Which expression is equivalent to 42ak+42ak, where k>0?

A.

84ak

B.

84ak2k

C.

42ak+1k

D.

42ak2+1k

Which expression is equivalent to 42 a k + 42 a k , where k >

Hard-difficulty · SAT Math · Equivalent Expressions — Simplifying polynomials. Read the question above, select your answer, and check the full explanation below to understand exactly why the correct choice works.

Answer explanation

Choice D is correct. Two fractions can be added together when they have a common denominator. Since k>0, multiplying the second term in the given expression by kk yields 42akkk, which is equivalent to 42ak2k. Therefore, the expression 42ak+42ak can be written as 42ak+42ak2k which is equivalent to 42a+42ak2k. Since each term in the numerator of this expression has a factor of 42 a , the expression 42a+42ak2k can be rewritten as 42a1+42ak2k, or 42a1+k2k, which is equivalent to  42a(k2+1)k.

Choice A is incorrect. This expression is equivalent to 42ak + 42ak.

Choice B is incorrect and may result from conceptual or calculation errors.

Choice C is incorrect. This expression is equivalent to 42ak + 42a.