Coefficients:
            Estimate Std. Error t value Pr(>|t|)
(Intercept)  1.08750    0.78832   1.380   0.2102
x           -0.30873    0.32923  -0.938   0.3796
I(x^2)       0.07142    0.02917   2.449   0.0442 *

Model 1: y ~ x
Model 2: y ~ x + I(x^2)
  Res.Df    RSS Df Sum of Sq      F Pr(>F)
1      8 5.8381
2      7 3.1446  1    2.6934 5.9956 0.0442 *

x <- 1:10
set.seed(17)
y <- 0.2 * x + rnorm(length(x))
z <- y + 2.535153*(x/5-1)^2