Question

If a+b=10 and ab=21 find the value of a2-b2

Answer 1

Answer:

Step-by-step explanation:

Answer 2

Answer: 40 or -40

Step-by-step explanation:

Using the substitution method,

a+b = 10 so a = 10 - b

We can plug this in the second equation.

(10-b)b=21

10b - $b^{2}$ = 21

$b^{2}$+10b - 21 = 0

(b - 7 ) (b -3 ) = 0

b = 7 and b =3

If b is 7, then a is 3.

If b is 3 then a is 7

So it is either 49-9 = 40

or 9 - 49 = -40