find zero of f(x)=x^2+2x-15
x ²+2x-15factorize the equation (x+5)(x-3)therefore the zeros are -5 and 3
\(f(x)=x^2+2x-15\\\\f(x)=0\iff x^2+2x-15=0\\\\x^2+5x-3x-15=0\\\\x(x+5)-3(x+5)=0\\\\(x+5)(x-3)=0\iff x+5=0\ or\ x-3=0\\\\\boxed{x=-5\ and\ x=3}\leftarrow zeros\)