Question

Using suitable Identity, get the product : (x-4)(x+7) .​

Answer 1

(x-4)(x+7)

identity : (x+a)(x+b) = x² + x(a+b) + ab

(x-4)(x+7)

= x² + x(-4+7) + (-4)(7)

= x² + x(3) - 28

x² + 3x - 28

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Answer 2

$\huge \sf \underline \red{Answer : }$

$\: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \implies \rm \purple{ {x}^{3} + 3x -28 }$

$\huge \sf \underline \pink{Given : }$

$\: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \sf{(x - 4)(x + 7)}$

$\: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \implies \sf \blue{ (x - 4)(x + 7)}$

$\: \: \: \sf \underline{we \: know \: that \: formula}$

$\bf{ \boxed{ \underline{ \underline{ \red{ \tt{(x + a)(x + b) = {x}^{2} + (a + b) + ab \: }}}}}}$

$\: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \implies \sf \blue{ (x + ( - 4))(x + 7)}$

$\: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \implies \sf \blue{ {x}^{2} + ( - 4 + 7)x + ( - 4) \times (7) }$

$\: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \implies \sf \blue{ {x}^{3} + 3x -28 }$