curve(f,-3,3,col='red')
abline(h=-0)

f=function(x) {1/sqrt(2*pi)*exp(-x^2/2)}
integrate(f,-Inf,Inf)

f=function(x) {(x^2)*sin(2*x)}
integrate(f,0,pi)

f=function(x) {1/(1+x^2)}
integrate(f,-Inf,Inf)

f=function(x) {(6*x)^2+((7/2)*x)-5}
curve(f,-2,2)

f=function(x) {6*x^2+7/2*x-5}
curve(f,-2,2)
g=function(x) {-12*x^2-7*x+13}
curve(g,-2,2,add=TRUE,col='red')
h=function(x) {g(x)-f(x)} #f pomocnicza
curve(h,-2,2,add=TRUE,col='red')
library(rootSolve)
x0=uniroot.all(h,c(-2,2)) #pkt przeciecia
integrate(h,x0[1],x0[2]) #pole