To find the coefficients of x and x2 in the expansion of (2 + ax)7, we use the binomial theorem.
The general term in the expansion is given by:
\(\binom{7}{r} (2)^{7-r} (ax)^r\)
\(For the coefficient of x, set r = 1:\)
\(\binom{7}{1} (2)^6 (ax) = 7 \times 2^6 \times a \times x\)
The coefficient is \(7 \times 2^6 \times a\).
\(For the coefficient of x2, set r = 2:\)
\(\binom{7}{2} (2)^5 (ax)^2 = 21 \times 2^5 \times a^2 \times x^2\)
The coefficient is \(21 \times 2^5 \times a^2\).
Since the coefficients are equal, we have:
\(7 \times 2^6 \times a = 21 \times 2^5 \times a^2\)
Simplifying gives:
\(7 \times 2 = 21 \times a\)
\(a = \frac{2}{3}\)