He made a mistake in step #2. It seemed to be a trivial mistake because it involved signs, but it still had a great impact. Since step#2, his solution was already wrong.
Instead of
(-1)²-4(2)(-6) = 1 + 48 = 49
What he did is
(-1)²-4(2)(-6) = -1 + 48 = 47
The solution is x=1 and y=-2
Further explanation:
Given equations are:

Multiplying equation no. 1 with 2 will give us:
Eqn 3
From equation no 2:

Putting the value of y in eqn 3

The solution is x=1 and y=-2
Keywords: Linear equations, Solution set
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1. 2x^2-x-15=0
A = 2
B = -1
C = -15
2. 10^2-2x=0
A = 10
B = -2
C = 0
3. x^2–3x-40=0
A = 1
B = -3
C = -40
4. x^2+3x-2=0
A = 1
B = 3
C = -2
5. 4x^2-17x+8=0
A = 4
B = -17
C = 8
Remember the equations should look like Ax^2+Bx+C=0 (in this order!!)
Answer:

Step-by-step explanation:
Surface area of cylinder = 2πr(h + r)
Volume of cylinder = πr²h
Given that S.A = Volume of the cylinder, therefore, we have:
2πr(h + r) = πr²h
Radius (r) is given as 2.5 cm
height (h) = x cm
Input the values and solve for x
2πr(h + r) = πr²h
2πr(h + r) = πr(rh)
2(h + r) = rh (πr cancels πr)


Subtract 2x from both sides


Divide both sides by 0.5


