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CEMC Euclid, 2025

Algebra Difficulty 1.0 Junior Prove it Canada

If 4(x−2)=2(x−4)4(x-2) = 2(x-4), what is the value of xx?
If 2x=92x = 9, what is the value of 26x−232^{6x-23}?
Determine the coordinates of the point of
intersection of the lines with equations y=3x+7y = 3x + 7 and y=7x+3y = 7x + 3.

Solution

Since 4(x−2)=2(x−4)4(x-2) = 2(x-4), then
4x−8=2x−84x - 8 = 2x - 8 which gives 2x=02x = 0 and so x=0x=0.
Solution 1:

If 2x=92x = 9, then 6x=3⋅2x=3⋅9=276x = 3 \cdot 2x = 3 \cdot 9 = 27.

This means that 26x−23=227−23=24=162^{6x-23} = 2^{27 - 23} = 2^4 = 16.

Solution 2:

If 2x=92x = 9, then x=92x = \frac{9}{2}.

Therefore, 6x−23=6⋅92−23=27−23=46x - 23 = 6 \cdot \tfrac{9}{2} - 23 = 27 - 23 = 4.

Thus, 26x−23=24=162^{6x - 23} = 2^4 = 16.
Equating expressions for yy,
we obtain 3x+7=7x+33x + 7 = 7x + 3, which
gives 4=4x4 = 4x and so x=1x = 1.

Since x=1x = 1, then y=3x+7=3+7=10y = 3x + 7 = 3 + 7 = 10, and so the point
of intersection has coordinates (1,10)(1, 10).

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