Question

If a+b=5 a-b=3 find ab

Answer 1

a+b=5
a-b=3
solving 1 and 2
2a=8
a=4
by substituting a value we get b=1
ab=4
hope it helps
please mark it as brainliest

Answer 2

Given:

a + b = 5 and  a - b = 3

We have to find the value of ab = ?

Solution:

Using the trigonometric identity:

$(a+b)^{2})-(a-b)^{2}=a^{2} +b^{2}+2ab-( a^{2} +b^{2}-2ab)$

⇒ $(a+b)^{2})-(a-b)^{2}=a^{2} +b^{2}+2ab-a^{2} b^{2}+2ab$

⇒ $(a+b)^{2})-(a-b)^{2}$ = 4ab      ........ (1)

Put a + b = 5 and  a - b = 3, we get

4ab = $(5)^{2})-(3)^{2}$

⇒ 4ab =25 - 9

⇒ 4ab = 16

⇒ ab = $\dfrac{16}{4}$

⇒ ab = 4

∴ ab = 4

Thus, the value of "ab is equal to 4".