Question

Y^2-10+30 Prove that the value of the expression must be positive.

Answer 1

Explanation:

`y^2-10y+30=\\y^2-2(y)(5)+5^2-5^2+30=\\(y-5)^2-25+30=\\(y-5)^2+5`

`(y-5)^2\geq 0\\\Rightarrow\ (y-5)^2+5 > 0\\Thus,\ y^2-10y+30 > 0`