Question

find 85 square by using (a+b)square =a square +2ab +b square
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Answer 1

Answer:

the answer is 721

Step-by-step explanation:

a - b = 7 ...given equation 1......

( a - b)² = a² + b² - 2ab

49 = 85 - 2ab

the value of a² + b² is 85 given

by here the value of 2ab is 36

now ( a + b) ² = a² + b² + 2ab

= 85 + 36

( a + b)² = 121

a + b = 11 equation 2.......

now add equation for 1 and 2, I we get

a = 9

b = 2

now the value of a³- b³

= 9³ - 2³

= 721 ans

Answer 2

Step-by-step explanation:

$given \: that \: {85}^{2} \\ \: it \: can \: be \: written \: as \: (80 + 5) ^{2} \\ \: it \: is \: in \: the \: form \: of \: (a + b) ^{2} \\ \: </p><p>we \: know \: that \: {(a + b)}^{2} = {a}^{2} + 2ab + {b}^{2} \\ \: (80 + 5) ^{2} = {80}^{2} + 2 \times 80 \times 5 + {5}^{2} \\ \: = > 6400 + 800 + 25 \\ \: = > 7225 \\ \: {85}^{2} = 7225$