Answer:
c. 7x^2+168x+144
Step-by-step explanation:
[tex]\bold{METHOD\ 1}\\\\(7x+12)^2\qquad\text{use}\ (a+b)^2=a^2+2ab+b^2\\\\=(7x)^2+(2)(7x)(12)+12^2=49x^2+168x+144\\\\\bold{METHOD\ 2}\\\\(7x+12)^2=(7x+12)(7x+12)\\\text{use}\ FOIL:\ (a+b)(c+d)=ac+ad+bc+bd\\\\=(7x)(7x)+(7x)(12)+(12)(7x)+(12)(12)\\\\=49x^2+84x+84x+144\qquad\text{combine like terms}\\\\=49x^2+(84x+84x)+144=49x^2+168x+144[/tex]
