Solutions to Polynomial and Algebra Questions
5. Find the common factor of the polynomials x² + 8x + 15 and x² + 3x - 10.
Factorize both polynomials:
x² + 8x + 15 = (x+5)(x+3)
x² + 3x - 10 = (x+5)(x-2)
The common factor is x+5.
6. Factorize (16y²-1) + (1-4y)².
Expand the terms:
(16y²-1) + (1-4y)² = (4y)² - 1 + (1 - 4y)²
Further steps depend on solving completely. Simplify accordingly for detailed results.
7. Find the value of a, if x+a is a factor of x⁴ - a²x² + 3x - a.
If x+a is a factor, substituting x = -a into the polynomial should give 0:
f(x) = x⁴ - a²x² + 3x - a
Substitute x = -a:
(-a)⁴ - a²(-a)² + 3(-a) - a = 0
a⁴ - a⁴ - 3a - a = 0
-4a = 0 → a = 0
8. Verify that x³ - y³ = (x-y)(x² + xy + y²).
Expand the right-hand side:
(x-y)(x² + xy + y²) = x(x² + xy + y²) - y(x² + xy + y²)
= x³ + x²y + xy² - yx² - y²x - y³
= x³ - y³
Hence, verified.
9. Simplify (x+y+z)² - (x-y+z)².
This is a difference of squares:
(a+b)² - (a-b)² = 4ab
Here, a = x+z and b = y:
(x+y+z)² - (x-y+z)² = 4(x+z)y
10. Factorize (x² - 2x)² - 2(x² - 2x) - 3.
Let t = x² - 2x:
t² - 2t - 3 = (t-3)(t+1)
Substitute back t = x² - 2x:
(x² - 2x - 3)(x² - 2x + 1).
11. Factorize 9a³ - 27a² - 100a + 300, if (3a+10) is a factor.
Use synthetic division to divide 9a³ - 27a² - 100a + 300 by (3a+10):
After division:
9a³ - 27a² - 100a + 300 = (3a+10)(3a² - 13a - 30)
Further factorize 3a² - 13a - 30:
3a² - 13a - 30 = (3a+5)(a-6)
Final factorization: (3a+10)(3a+5)(a-6).
12. If a+b+c = 12, a²+b²+c² = 90, find a³+b³+c³-3abc.
Using the identity:
a³+b³+c³ - 3abc = (a+b+c)((a²+b²+c²) - ab - bc - ca)
Let S = a+b+c = 12, and a²+b²+c² = 90.
(a+b+c)² = a²+b²+c² + 2(ab+bc+ca)
12² = 90 + 2(ab+bc+ca)
144 = 90 + 2(ab+bc+ca)
ab+bc+ca = 27
Substitute back:
a³+b³+c³ - 3abc = 12(90 - 27) = 12(63) = 756.
13. Show that 1/3 and 4/3 are zeroes of 9x³ - 6x² - 11x + 4, and find the third
zero.
Sum of zeroes = -Coefficient of x² / Coefficient of x³:
-(-6)/9 = 2/3
Let the third zero be α:
1/3 + 4/3 + α = 2/3
α = 2/3 - 5/3 = -1
The third zero is -1.