Question the-ex

2.4 Equivalent Expressions - Simplifying polynomials
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The expression 635x455·28x8 is equivalent to a x b , where a and b are positive constants and x>1. What is the value of a + b ?

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The expression 6 3 5 x 45 5 · 2 8 x 8 is equivalent to

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

The correct answer is 3618. The rational exponent property is ymn=ymn, where y>0, m and n are integers, and n>0. This property can be applied to rewrite the given expression 635x455·28x8 as 6355x455288x18, or 63x92x18. This expression can be rewritten by multiplying the constants, which gives 36x9x18. The multipliion exponent property is yn·ym=yn+m, where y>0. This property can be applied to rewrite the expression 36x9x18 as 36x9+18, or 36x738. Therefore, 635x455·28x8=36x738. It's given that 635x455·28x8 is equivalent to axb; therefore, a=36 and b=738. It follows that a+b=36+738. Finding a common denominator on the right-hand side of this equation gives a+b=2888+738, or a+b=3618. Note that 361/8, 45.12, and 45.13 are examples of ways to enter a correct answer.