1, using the complete square formula (a+b) 2 = a 2+2ab+b 2. (a-b) 2 = a 2-2ab+b 2。

(a+b)2-(a-b)2 = a2+B2+2ab-(a2+B2-2ab)= 4ab。 Bring 7 and 4 into ab=4\3.

Similarly, (a+b) 2+(a-b) 2 = 2a 2+2b 2. The solution is a 2+b 2 = 1 1 \ 2.

2, or use the complete square formula, (a+b) 2 = a 2+b 2+2ab = 5+4 = 9.

(a-b)^2=a^2+b^2-2ab=5-4= 1

(2 stands for square, \ stands for division, which is also a fractional line, and \ is preceded by numerator)

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