Which is the complete expansion of ( (x+7)^2 )?

Correct answer: \(x^2+14x+49\)

Using the identity \((a+b)^2=a^2+2ab+b^2\), put \(a=x\) and \(b=7\). Then \((x+7)^2=x^2+2\times x\times7+7^2=x^2+14x+49\). Hence, option A is correct. In option B, the middle term is written as \(7x\) instead of \(2ab=14x\). Exam tip: while expanding a squared binomial, always check the sign and coefficient of the \(2ab\) term.