✔ 最佳答案
Given Quadratic Equation in standard form :
y^2 +5y-14 =0
We can facorize the LHS expression by Method
of spilitting of Middle Term =>Their Product=(7y)x(-2y)= - 14
& Their Sum => (7y)+(--2y)= 5y
Hence, y^2+7y --2y--14 = 0
Or, y( y + 7) --2( y+ 7)= 0
Or, (y+7) (y-2)=0
By Zero Factor Theorem=> y+7=o=> y= -7
& y-2 = 0 => y=2
Thus,positive value of y=2 ,Negative value of y= --7
_________________________________________________Alternatively,Using Omar Khayyam's Quadratic Formula:
y= [ -b +( b^2-4ac)^ 1/2]/2a & y=[-b -(b^2-4ac) ^1/2/2a
a=1,b=5,c=-14=> y= [ -5+(25+56)^1/2]/2x1= 4^1/2=2
y= [-5 - ( 25 +56)^1/2]/2x1 =( -5-9)/2 = -7
Thus,postive value of y is 2 ,while negative value is --7