The slope of tangent to the curve x = t2 + 3t – 8, y = 2t2 – 2t – 5 at the point (2, –1) is:

Given equation of curve is x = t2 + 3t – 8, y = 2t2 – 2t – 5


x = t2 + 3t – 8


Differentiating on both sides with respect to t, we get



Applying the sum rule of differentiation, we get



We know derivative of a constant is 0, so above equation becomes



Applying the power rule we get



y = 2t2 – 2t – 5


Differentiating on both sides with respect to t, we get



Applying the sum rule of differentiation, we get



We know derivative of a constant is 0, so above equation becomes



Applying the power rule we get



Now we know,



Now substituting the values from equation (i) and (ii), we get



As given the curve passes through the point (2,-1), substituting these values in given curve equation we get


x = t2 + 3t – 8


2= t2 + 3t – 8


t2 + 3t – 8-2=0


t2 + 3t – 10=0


Splitting the middle term we get


t2 + 5t-2t – 10=0


t(t+ 5) -2(t+5)=0


(t+ 5) (t-2)=0


t+5=0 or t-2=0


t=-5or t=2……….(iii)


y = 2t2 – 2t – 5


-1=2t2 – 2t – 5


2t2 – 2t – 5+1=0


2t2 – 2t – 4=0


Taking 2 common we get


t2 – t – 2=0


Splitting the middle term we get


t2 – 2t +t– 2=0


⇒ t(t– 2)+1(t– 2)=0


⇒ (t– 2)(t+1)=0


⇒ (t– 2)=0 or (t+1)=0


t=2 or t=-1……..(iv)


So from equation (iii) and (iv), we can see that 2 is common


So t=2


So the slope of the tangent at t=2 is given by






Therefore, the slope of tangent to the curve x = t2 + 3t – 8, y = 2t2 – 2t – 5 at the point (2, –1) is


So the correct option is option B.

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