Question

Plz help...........plz

Answer 1

a+2b=3.......(1)

ab=-5

b=-5/a.........(2)

sub 2 in 1

a+2(-5/a)=3

a+(-10/a)=3

a-10/a=3

${a}^{2} - 10 = 3a$

${a}^{2} - 3a - 10 = 0$

a(a)+2a-5a-5(2)

a(a+2)-5(a+2)

(a+2)(a-5)

therefore, a=-2 or a=5

sub a =5 in (2)

therefore, b=-1

${a}^{2} + 4 {b}^{2} = {5}^{2} + 4 { ( - 1)}^{2}$

=25+4(1)

=25+4

=29

${a}^{3} + 8 {b}^{3} = {5}^{3} + 8( { - 1)}^{3}$

=125+8(-1)

=125-8

=117

hope it will help you....