Mixed: contest blend

Questions at easy, medium and hard levels. Pick a level and get a fresh set every time, with instant feedback.

Learn it Contest problems reward clever shortcuts: difference of squares $a^2 - b^2 = (a + b)(a - b)$, $(x + y)^2 = x^2 + 2xy + y^2$, and patterns in units digits.

Example: $x + y = 7$ and $xy = 10$. Find $x^2 + y^2$.

$(x + y)^2 = x^2 + 2xy + y^2$.
$49 = x^2 + y^2 + 20$.
$x^2 + y^2 = 29$.

Loading questions…