Maths Olympiad Prep

Track / Stage 4 / 86 of 340 #346 of 1964

Problem 346

AMC 12 late, AIME early
Algebra Difficulty 4.6 Find the answer

If (y5)2=(y9)2(y-5)^{2}=(y-9)^{2}, what is the value of yy ?

A number or a short expression. Fractions can be typed as 3/2, and spacing doesn't matter.

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Official solution

Expanding both sides, we have y210y+25=y218y+81y^{2}-10 y+25=y^{2}-18 y+81.

Rearranging, we have 8y=568 y=56, so y=7y=7.

Source: NuminaMath-1.5, licensed Apache-2.0. Statement reproduced verbatim; metadata (topic, difficulty, ordering) added by this project.