
Given: 
(a + b)^{7} = _{7}C_{0}a^{7} + _{7}C_{1}a^{6}b + _{7}C_{2}a^{5}b^{2} + _{7}C_{3}a^{4}b^{3} + _{7}C_{4}a^{3}b^{4} + _{7}C_{5}a^{2}b^{5} + _{7}C_{6}ab^{6} + _{7}C_{7}b^{7} 

Expand: 
(3x  1)^{7} 

Section 1: First, substitute values for coefficients, the avalue, and the bvalue. 
(3x  1)^{7} =


Section 2: Next, write the correct final coefficients. 
(3x  1)^{7} = x^{7} + x^{6} + x^{5} + x^{4} + x^{3} + x^{2} + x + 

