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Subcontests

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1967 MMPC , Part 2 = Michigan Mathematics Prize Competition

p1. Consider the system of simultaneous equations (x+y)(x+z)=a2(x+y)(x+z)=a^2 (x+y)(y+z)=b2(x+y)(y+z)=b^2 (x+z)(y+z)=c2(x+z)(y+z)=c^2 , where abc0abc \ne 0. Find all solutions (x,y,z)(x,y,z) in terms of aa,bb, and cc.
p2. Shown in the figure is a triangle PQRPQR upon whose sides squares of areas 1313, 2525, and 3636 sq. units have been constructed. Find the area of the hexagon ABCDEFABCDEF . https://cdn.artofproblemsolving.com/attachments/b/6/ab80f528a2691b07430d407ff19b60082c51a1.png
p3. Suppose p,qp,q, and rr are positive integers no two of which have a common factor larger than 11. Suppose P,QP,Q, and RR are positive integers such that Pp+Qq+Rr\frac{P}{p}+\frac{Q}{q}+\frac{R}{r} is an integer. Prove that each of P/pP/p, Q/qQ/q, and R/rR/r is an integer.
p4. An isosceles tetrahedron is a tetrahedron in which opposite edges are congruent. Prove that all face angles of an isosceles tetrahedron are acute angles. https://cdn.artofproblemsolving.com/attachments/7/7/62c6544b7c3651bba8a9d210cd0535e82a65bd.png
p5. Suppose that p1p_1, p2p_2, p3p_3 and p4p_4 are the centers of four non-overlapping circles of radius 11 in a plane and that, pp is any point in that plane. Prove that p1p2+p2p2+p3p2+p4p26.\overline{p_1p}^2+\overline{p_2p}^2+\overline{p_3p}^2+\overline{p_4p}^2 \ge 6.

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