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4 years ago

Solve x2 - 8x = 20 by completing the square. Which is the solution set of the equation?

Mathematics

1 answer:

Artyom0805 [142]4 years ago

3 0

Answer:

{-2,10}

Step-by-step explanation:

x^2 - 8x = 20

Take the coefficient of x

-8

Divide by 2

-8/2 =-4

Square it

(-4)^2 =16

Add this to each side

x^2 - 8x+16 = 20+16

x^2 - 8x+16 = 36

The left hand side becomes( x + (-8/2) )^2

(x - 4)^2 = 36

Take the square root of each side

sqrt((x - 4)^2) =±sqrt( 36)

x-4 = ±6

Add 4 to each side

x-4+4 = 4±6

x = 4±6

x = 4+6 x = 4-6

x = 10 x = -2

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7x^2=9+x what are the values of x Will give medal and points

DENIUS [597]

7x² = 9 + x Subtract x from both sides
7x² - x = 9 Subtract 9 from both sides
7x² - x - 9 = 0 Use the Quadratic Formula

a = 7 , b = -1 , c = -9

x = $\frac{-b \pm \sqrt{b^2 - 4ac} }{2a}$ Plug in the a, b, and c values
x = $\frac{- (-1) \pm \sqrt{(-1)^2 - 4(7)(-9)} }{2(7)}$ Cancel out the double negative
x = $\frac{1 \pm \sqrt{(-1)^2 - 4(7)(-9)} }{2(7)}$ Square -1
x = $\frac{1 \pm \sqrt{1 - 4(7)(-9)} }{2(7)}$ Multiply 7 and -9
x = $\frac{1 \pm \sqrt{1 - 4(-63} }{2(7)}$ Multiply -4 and -63
x = $\frac{1 \pm \sqrt{1 + 252} }{2(7)}$ Multiply 2 and 7
x = $\frac{1 \pm \sqrt{1 + 252} }{14}$ Add 1 and 252
x = $\frac{1 \pm \sqrt{253} }{14}$ Split up the $\pm$
x = $\left \{ {{ \frac{1 + \sqrt{253} }{14} } \atop { \frac{1 - \sqrt{253} }{14} }} \right.$
The approximate square root of 253 is 15.905973.
x ≈ $\left \{ { \frac{1 + 15.905973}{14} } \atop { \frac{1 - 15.905973}{14} }} \right$ Add and subtract
x ≈ $\left \{ {{ \frac{16.905973}{14} } \atop { \frac{14.905973}{14} }} \right.$ Divide
x ≈ $\left \{ {{1.2075} \atop {1.0647}} \right.$ Round to the nearest hundredth
x ≈ $\left \{ {{1.21} \atop {1.06}} \right.$

7 0

3 years ago

Write an algebraic expression for the word phrase. five fewer than d days d – 5 5 + d 5 – d d + 5

Troyanec [42]

Answer:

(d-5)

Step-by-step explanation:

we know that

The phrase"five fewer than d days" is equal to subtract 5 from the number d

d minus 5-----> (d-5)

7 0

3 years ago