1) cube root of 12x^2 ( cube root of 126x^2)
2) Find the zeros of y = x^3 -11x^2+ 41x - 51
Please show your steps!
2) Find the zeros of y = x^3 -11x^2+ 41x - 51
Please show your steps!
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Cube root of 126x² is in its simplest form
Could it have been cube root of 128x²
because 128 = 64 x 2
......................................…
so cube root of 128x² = 4\³/(2x²)
Now to get zeros of x² -11x² +41x-51
we shall first note that 51 = 17x3
then determine if 1 or -1 is a zero
when x=1
y=1³-11(1)² +41(1)-51 = 1-11+41-51 = -10+41-51=-20
lets try x=-1 giving us
y=(-1)³-11(1)² +41(-1)-51 = -1-11-41-51 = -12-41-51 which is definitely a negative number
let us now try x=3
y=(3)³-11(3)² +41(3)-51 = 27 -99+ 123-51=66 =0
boom! That is a zero. x=3 is one of the zeros and
x-3 is a factor
divide x³ -11x² +41x-51 by x -3
......x²..-8x..+17
...._______________
x-3)x³ -11x² +41x-51
.....x³ - 3x²......↓..Subtract this bring down
....————...........the 41x
..........-8x² + 41x
..........-8x²..+24x Subtract this then bring down
........————...........the 51
...................17x - 51
...................17x - 51 subtract this
..................————
.........................zero remainder
so
x²..-8x..+17 is quotient
the other zeroes can be obtained by completing
the square or using quadratic formula
If we complete square on
x²..-8x..+17 = 0
we get
x²..-8x. . = -17
x² - 8x + 16 = -17 + 16 = -1
so
(x+ 4)² = -1
thus
x+4 = ±i
so
x = -4+i or x= -4-i
thus all zeros, including complexes are
x=3, x=-4+i , x= -4-i
Could it have been cube root of 128x²
because 128 = 64 x 2
......................................…
so cube root of 128x² = 4\³/(2x²)
Now to get zeros of x² -11x² +41x-51
we shall first note that 51 = 17x3
then determine if 1 or -1 is a zero
when x=1
y=1³-11(1)² +41(1)-51 = 1-11+41-51 = -10+41-51=-20
lets try x=-1 giving us
y=(-1)³-11(1)² +41(-1)-51 = -1-11-41-51 = -12-41-51 which is definitely a negative number
let us now try x=3
y=(3)³-11(3)² +41(3)-51 = 27 -99+ 123-51=66 =0
boom! That is a zero. x=3 is one of the zeros and
x-3 is a factor
divide x³ -11x² +41x-51 by x -3
......x²..-8x..+17
...._______________
x-3)x³ -11x² +41x-51
.....x³ - 3x²......↓..Subtract this bring down
....————...........the 41x
..........-8x² + 41x
..........-8x²..+24x Subtract this then bring down
........————...........the 51
...................17x - 51
...................17x - 51 subtract this
..................————
.........................zero remainder
so
x²..-8x..+17 is quotient
the other zeroes can be obtained by completing
the square or using quadratic formula
If we complete square on
x²..-8x..+17 = 0
we get
x²..-8x. . = -17
x² - 8x + 16 = -17 + 16 = -1
so
(x+ 4)² = -1
thus
x+4 = ±i
so
x = -4+i or x= -4-i
thus all zeros, including complexes are
x=3, x=-4+i , x= -4-i
-
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