Question

if alpha and beta are the Root's of x square plus 5x minus 1 is equal to 0. then find the value of alpha cube plus beta cube.​

Answer 1

Answer:

alpha³+beta³=-140

Step-by-step explanation:

Alpha and beta are roots of followers equation:

x²+5x-1=0

comparing with ax²+bx+c=0,

a=1,b=5,c=-1

alpha+beta = -b/a = -5/1=-5

alpha×beta= c/a =-1/1=-1

thus value of alpha³+beta³=

(alpha +beta) (alpha²-alpha×Beta +beta²)

= (-5)(alpha²+beta²-alpha×beta)

= (-5) ((alpha +beta)²-2alpha×beta-alpha×beta)

(because (a+b)²= a²+b²+2ab ; a²+b²=(a+b)²-2ab)

= (-5)((-5)²-3(alpha×beta))

= (-5)(25-3(-1))

= (-5)(25+3)

= (-5)(28)

= -140

I hope this will help you.....

Answer 2

it's explain in photo Thank you !