Question

fie f:R cu valori in R, f(x)=4x la puterea adoua +5x-9. Sa se detrmine punctele de intersectie ale graficului functiei f cu axa Ox.

Answer 1

f(x) = 4x^2+5x-9

Gf∩Ox => y = 0 => f(x) = 0

4x^2+5x-9=0

Δ=5^2-4*4*(-9) = 25 + 144 = 169

$x_{1,2}=\frac{-5+/-\sqrt{169}}{8}\\x_{1} = \frac{-5+\sqrt{169}}{8}=\frac{-5+13}{8}=1=> A(1,0)\\x_{2} = \frac{-5-\sqrt{169}}{8}=\frac{-5-13}{8}=\frac{-18}{8}=\frac{-9}{4}=>B(\frac{-9}{4},0)$