How do you solve $x^{2} + 2 x - 15 = 0$ $x^2 + 2x - 15 = 0$ ?

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How do you solve $x^{2} + 2 x - 15 = 0$ $x^2 + 2x - 15 = 0$ ?

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Answer 1 · 2018-04-12T14:35:40

$x = - 5 or x = 3$ $x=-5" or "x=3$

Explanation:

$the factors of - 15 which sum to + 2 are + 5 and - 3$ $"the factors of - 15 which sum to + 2 are + 5 and - 3"$

$\Rightarrow (x + 5) (x - 3) = 0$ $rArr(x+5)(x-3)=0$

$equate each factor to zero and solve for x$ $"equate each factor to zero and solve for x"$

$x + 5 = 0 \Rightarrow x = - 5$ $x+5=0rArrx=-5$

$x - 3 = 0 \Rightarrow x = 3$ $x-3=0rArrx=3$

Answer 2 · 2018-04-12T14:50:40

$x = - 5 or 3$ $x=-5 or 3$

Explanation:

Rules for factorising:

$a x^{2} + b x + c = 0$ $ax^2+bx+c=0$
$m \times n = c$ $m xx n = c$
$m + n = b$ $m + n = b$
$:.(x+m)(x+n) = 0$

In this case:

$5 xx -3 = -15 = c$

$5 + -3 = 2 = b$

$:. x^2+2x−15=0 -> color(red)((x+5)(x-3) = 0)$

Either of the brackets must be equal to 0.

Assuming (x+5) = 0:

$color(red)(x=-5)$

Assuming (x-3) = 0:

$color(red)(x=3)$

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How do you solve $x^{2} + 2 x - 15 = 0$ $x^2 + 2x - 15 = 0$ ?

2 Answers

Explanation:

Explanation:

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How do you solve x^2 + 2x - 15 = 0 x2+2x−15=0x^2 + 2x - 15 = 0 ?

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How do you solve $x^{2} + 2 x - 15 = 0$ $x^2 + 2x - 15 = 0$ ?