Given function :
[tex]f(x)=x^2+2x[/tex]We need to find the value of f(3) -7
substitute the value of x=3 in the given expression and then subtract 7 from it
[tex]\begin{gathered} f(x)=x^2+2x \\ \text{for x=3,} \\ f(3)=3^2+2(3) \\ f(3)=9+6 \\ f(3)=15 \\ \text{ Since, we have to find the value of f(3)-7} \\ \text{subtitute the value of f(3) and simplify} \\ f(3)-7=15-7 \\ f(3)-7=8 \end{gathered}[/tex]Answer : f(3)-7 = 8
