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Algebra Difficulty 1.3 Junior Find the answer

The operation \nabla is defined by ab=4a+ba \nabla b=4 a+b. What is the value of (52)2(5 \nabla 2) \nabla 2?

A number or a short expression. Spacing and $ signs are ignored.

Solution

Using the definition, (52)2=(4×5+2)2=222=4×22+2=90(5 \nabla 2) \nabla 2=(4 \times 5+2) \nabla 2=22 \nabla 2=4 \times 22+2=90.

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