f(x)=x7+5x3+3x+1
For number of real solutions, we need to find the number of times the curve cuts x−axis.
Now f′(x)=7x6+15x2+3>0
∴f(x) is strictly increasing function

i.e. when x→−∞,y→−∞ and when x→∞,y→∞
So, the curve will cut x−axis only once.
∴ number of real solution will be 1