Question

$if(a + b) =4 \: and \: {a}^{2}+ {b}^{2} = 7 \\ then \: the \: value \: of \: ab \: is \:$
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Answer 1

Step-by-step explanation:

This is the answer

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Answer 2

Given :-

• (a + b) = 4
• a² + b² = 7

To find :-

• Value of ab = ?

Solution :-

For solving this type of questions, we need to apply the below mentioned formula:

(a + b)² = a² + b² + 2ab

Now substitute (a + b) as 4 and a² + b² as 7

⇒ (4)² = 7 + 2ab

Since 4² is 16,

⇒ 16 = 7 + 2ab

⇒ 2ab = 16 - 7

⇒ 2ab = 9

⇒ ab = 9/2

∴ ab = 4.5

Know more:

$\boxed{\begin{minipage}{7 cm}\boxed{\bigstar\:\:\textbf{\textsf{Algebric\:Identity}}\:\bigstar}\\\\1)\bf\:(A+B)^{2} = A^{2} + 2AB + B^{2}\\\\2)\sf\: (A-B)^{2} = A^{2} - 2AB + B^{2}\\\\3)\bf\: A^{2} - B^{2} = (A+B)(A-B)\\\\4)\sf\: (A+B)^{2} = (A-B)^{2} + 4AB\\\\5)\bf\: (A-B)^{2} = (A+B)^{2} - 4AB\\\\6)\sf\: (A+B)^{3} = A^{3} + 3AB(A+B) + B^{3}\\\\7)\bf\:(A-B)^{3} = A^{3} - 3AB(A-B) + B^{3}\\\\8)\sf\: A^{3} + B^{3} = (A+B)(A^{2} - AB + B^{2})\\\\\end{minipage}}$