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4) If the zeroes of the
quadratic polynomial x² + (a + 1)x + b are 2 and -3,then find the
value of a and b


Sagot :

Answer:

  • a = 0
  • b = -6

Step-by-step explanation:

We can the value of a and b by using the factor theorem, where:

"If a is a zero of a polynomial f(x), then one of its factors is (x - a) and f(a) = 0"

Given that the zeros for f(x) = x² + (a + 1)x + b are 2 and -3, then:

  • f(2) = 0
  • f(3) = 0

for f(2) = 0:

[tex]f(2)=0[/tex]

[tex]2^2+(a+1)(2)+b=0[/tex]

[tex]4+2a+2+b=0[/tex]

[tex]2a+b=-6\ \text{ ... [1]}[/tex]

for f(-3) = 0:

[tex]f(-3)=0[/tex]

[tex](-3)^2+(a+1)(-3)+b=0[/tex]

[tex]9-3a-3+b=0[/tex]

[tex]-3a+b=-6\ \text{ ... [2]}[/tex]

Combining [1] & [2]:

[tex]\begin{aligned}\\2a+b&=-6\\-3a+b&=-6\\-----&----\ (-)\\5a&=0\\\bf a&=0\end{aligned}[/tex]

Substitute a = 0 into [1]

[tex]2a+b=-6[/tex]

[tex]2(0)+b=-6[/tex]

[tex]\bf b=-6[/tex]