Question

if a2 +b2 + +c2=29
and a+b+c =9
Find :-
ab+ bc+ ca​

Answer 1

Answer:

$a + b + c = 9$

$on \: squaring \: both \: sides$

$a {}^{2} + b {}^{2} + c {}^{2} + 2(ab + bc + ca) = 9 \times 9$

$2(ab + bc + ca) = 81 - (a {}^{2} + b {}^{2} + c {}^{2} )$

$2(ab + bc + ca) = 81 - 29$

$2(ab + bc + ca) = 52$

$ab + bc + ca = \frac{52}{2}$

$ab + bc + ca = 26$

hope it helps you dear

Answer 2

Step-by-step explanation:

Answer:

a + b + c = 9a+b+c=9

sidesonsquaringbothsides

a {}^{2} + b {}^{2} + c {}^{2} + 2(ab + bc + ca) = 9

2

+b

2

+c

2

+2(ab+bc+ca)=9×9

2(ab + bc + ca) = 81 - (a {}^{2} + b {}^{2} + c {}^{2} )2(ab+bc+ca)=81−(a

2

+b

2

+c

2

)

2(ab + bc + ca) = 81 - 292(ab+bc+ca)=81−29

2(ab + bc + ca) = 522(ab+bc+ca)=52

ab + bc + ca = \frac{52}{2}ab+bc+ca=

2

52

ab + bc + ca = 26ab+bc+ca=26