The perfect square pattern tells us that (a+b)²=a²+2ab+b². This can be used to expand (x+1)² as x²+2x+1, but also to expand (5x⁶+4)² as 25x¹²+40x⁶+16, or (3t²-7t⁶)² as 9t⁴-42t⁸+49t¹².
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