Question

factorise 25 -(y-4)²​

Answer 1

Answer:

$- {y}^{2} + 8y + 9$

or

$9 - {y}^{2} + 8y$

Step-by-step explanation:

given,

$= 25 - {(y - 4)}^{2}$

we know that,

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

$= 25 - ( {y}^{2} + {4}^{2} - 2 \times y \times 4)$

$= 25 - ( {y}^{2} + 16 - 8y)$

now removing brackets,

the '-' value changes to '+' and '+' value changes to '-' because, infront of brackets there is minus symbol.

$= 25 - {y}^{2} - 16 + 8y$

$= 25 - 16 - {y}^{2} + 8y$

$= 9 - {y}^{2} + 8y$

writing as increasing order of degrees,

$= - {y}^{2} + 8y + 9$

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