Here's the solution to Question 50, verifying the steps provided:
Question 50:
Given the equation: x2+px−10=0
Assume the roots are 2 and −5.
Find the value of p.
For a quadratic equation in the form ax2+bx+c=0, the following relationships hold for its roots r1 and r2:
- Sum of roots: r1+r2=−ab
- Product of roots: r1×r2=ac
From the given equation x2+px−10=0, we have:
a=1
b=p
c=−10
The assumed roots are r1=2 and r2=−5.
Step 1: Check the product of the roots.
The product of the given roots is:
r1×r2=2×(−5)=−10
Using the formula for the product of roots from the equation:
ac=1−10=−10
Since the calculated product matches the formula, the assumed roots are consistent with the constant term of the equation. (Note: The student's work incorrectly showed 2+(−5) for the product, but the result −10 was correct for the product).
Step 2: Calculate the sum of the roots.
The sum of the given roots is:
r1+r2=2+(−5)=−3
Step 3: Use the sum of roots formula to find p.
We know that the sum of roots is also equal to −ab.
r1+r2=−ab
Substitute the calculated sum and the values of a and b from the equation:
−3=−1p
−3=−p
Multiply both sides by −1:
p=3
Therefore, the value of p is 3.
The final answer is p=3.