Question

if a+b = -6 , a^2 + b^2 = 20 then ab =​

Answer 1

$\qquad\qquad\huge\underline{{\sf Answer}}$

By squaring the sum of two variables identity ~

$\qquad \sf  \dashrightarrow \:(a + b) {}^{2} = {a}^{2} + {b}^{2} + 2ab$

Now, plug in the given values ~

$\qquad \sf  \dashrightarrow \:( - 6) {}^{2} = 20 + 2ab$

$\qquad \sf  \dashrightarrow \:36 = 2(10 + ab)$

$\qquad \sf  \dashrightarrow \:10 + ab = 36 \div 2$

$\qquad \sf  \dashrightarrow \:10 + ab = 18$

$\qquad \sf  \dashrightarrow \:ab = 18 - 10$

$\qquad \sf  \dashrightarrow \:ab = 8$

I hope it was clear through my steps ~

Answer 2

Answer:

8

Step-by-step explanation:

(a+b)^2 = (-6)^2

a^2 + 2ab + b^2 = 36

a^2 + b^2 = 36 - 2ab

Equating 36 - 2ab with 20

36 - 2ab = 20

2ab = 16

ab = 8

Hope this helps out, feel free to mark this answer as brainliest :)