Alright Princess, let's tackle these.
Question 33: The sum of the coefficients in the expansion of (a+b)n is
Step 1: To find the sum of coefficients, substitute 1 for each variable in the expression.
For (a+b)n, substitute a=1 and b=1.
Sum of coefficients =(1+1)n=2n.
The sum of the coefficients is 2n.
This matches option c) 2n.
Question 34: In the expansion of (1+2x)6, the coefficient of x2 is
Step 1: Use the general term formula for binomial expansion: Tk+1=(kn)an−kbk.
Here, a=1, b=2x, and n=6.
We want the coefficient of x2, so we set k=2.
Step 2: Substitute k=2 into the formula.
T2+1=(26)(1)6−2(2x)2
T3=(26)(1)4(2x)2
Step 3: Calculate the binomial coefficient and simplify.
(26)=2!(6−2)!6!=2!4!6!=2×16×5=15
T3=15⋅1⋅(4x2)
T3=60x2
The coefficient of x2 is 60.
The coefficient of x2 is 60.
This matches option b) 60.
Question 35: The coefficient of x4 in the expansion of (1−x)6 is
Step 1: Use the general term formula: Tk+1=(kn)an−kbk.
Here, a=1, b=−x, and n=6.
We want the coefficient of x4, so we set k=4.
Step 2: Substitute k=4 into the formula.
T4+1=(46)(1)6−4(−x)4
T5=(46)(1)2(−x)4
Step 3: Calculate the binomial coefficient and simplify.
(46)=4!(6−4)!6!=4!2!6!=2×16×5=15
T5=15⋅1⋅x4
T5=15x4
The coefficient of x4 is 15.
The coefficient of x4 is 15.
This matches option c) 15.
Question 36: In the expansion of (2+3x)4, what is the coefficient of x2?
Step 1: Use the general term formula: Tk+1=(kn)an−kbk.
Here, a=2, b=3x, and n=4.
We want the coefficient of x2, so we set k=2.
Step 2: Substitute k=2 into the formula.
T2+1=(24)(2)4−2(3x)2
T3=(24)(2)2(3x)2
Step 3: Calculate the binomial coefficient and simplify.
(24)=2!(4−2)!4!=2!2!4!=2×14×3=6
T3=6⋅4⋅(9x2)
T3=6⋅4⋅9⋅x2
T3=216x2
The coefficient of x2 is 216.
The coefficient of x2 is 216.
Since 216 is not among options a) -72, b) -72, c) 36, d) -36, the correct option is e) None of the above.
Question 37: The coefficient of the term containing x2 in the expansion of (1+2x)−3 is
Step 1: Use the generalized binomial theorem for (1+y)n=1+ny+2!n(n−1)y2+3!n(n−1)(n−2)y3+…
Here, y=2x and n=−3.
We need the term containing x2, which corresponds to the term with y2.
Step 2: Substitute n=−3 and y=2x into the y2 term.
The term is 2!n(n−1)y2.
=2!(−3)(−3−1)(2x)2
=2×1(−3)(−4)(4x2)
=212(4x2)
=6(4x2)
=24x2
The coefficient of x2 is 24.
The coefficient of the term containing x2 is 24.
Since 24 is not among options a) -3, b) -6, c) 6, d) 3, the correct option is e) None of the above.
Question 38: The term independent of x in the expansion of (1−4x)5 is
Step 1: Use the general term formula: Tk+1=(kn)an−kbk.
Here, a=1, b=−4x, and n=5.
The term independent of x is the term where the power of x is 0. This occurs when k=0.
Step 2: Substitute k=0 into the formula.
T0+1=(05)(1)5−0(−4x)0
T1=(05)(1)5(1)
Step 3: Calculate the value.
(05)=1
T1=1⋅1⋅1=1
The term independent of x is 1.
The term independent of x is 1.
Since 1 is not among options a) -40, b) 40, c) -10, d) 10, the correct option is e) None of the above.
What's next?