Y=0.4x^2+2.5x+1.4

Solution for Y=0.4x^2+2.5x+1.4 equation:

=0.4Y^2+2.5Y+1.4

We move all terms to the left:

-(0.4Y^2+2.5Y+1.4)=0

We get rid of parentheses

-0.4Y^2-2.5Y-1.4=0

a = -0.4; b = -2.5; c = -1.4;
Δ = b2-4ac
Δ = -2.52-4·(-0.4)·(-1.4)
Δ = 4.01
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-2.5)-\sqrt{4.01}}{2*-0.4}=\frac{2.5-\sqrt{4.01}}{-0.8}
$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2.5)+\sqrt{4.01}}{2*-0.4}=\frac{2.5+\sqrt{4.01}}{-0.8}
$