\(a.\:\left(2x+3\right)^2-4\left(x-1\right)\left(x+1\right)=49\\ 4x^2+12x+9-4x^2+4=49\\ 12x=49-9\\ x=\dfrac{40}{12}=\dfrac{10}{3}\)
4x2 +12x+9-4(x2-1)=49
4x2+12x+9-4x+4=49
12x+13=49
12x=36
x=3
\(\left(2x+3\right)^2-4\left(x-1\right)\left(x+1\right)=49\)
\(\Rightarrow\left(2x+3\right)^2-\left(4x-4\right)\left(x+1\right)=49\)
\(\Rightarrow4x^2+12x+9-4x^2-4x+4x+4\)
\(\Rightarrow\left(4x^2-4x^2\right)+\left(4x-4x\right)+\left(4+9\right)+12x=49\)
\(\Rightarrow12x+13=49\Rightarrow12x=36\Rightarrow x=3\)
