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-4.9x^2+2x+21=0
a = -4.9; b = 2; c = +21;
Δ = b2-4ac
Δ = 22-4·(-4.9)·21
Δ = 415.6
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(2)-\sqrt{415.6}}{2*-4.9}=\frac{-2-\sqrt{415.6}}{-9.8} $$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(2)+\sqrt{415.6}}{2*-4.9}=\frac{-2+\sqrt{415.6}}{-9.8} $
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