Thread: Quadratic equation by factorisation (without using the standard formula)?

X2 -4x -165 = 0


must show that you have checked your answer by substituting the values obtained into the original expression

show each step of the solution,

Thanks

The equation can be factorized by inspection. The two numbers in the brackets must multiply together to make -165, so.....

If you find all the prime factors of 165, they are 3, 5, and 11. and note that 3x5 = 15

You also know that the sum of the two numbers in the brackets must be -4.

and.....
11x-15=-165
11+(-15)=-4

x^2-4x-165 = (x+11)(x-15)

this may sound like a silly question but am new on here, what does this symbol represent (^), thanks for your help mate. is your answer to my question the fully solved answer??

yer mate thats the answer. The ^ means 'to the power of'

so x^2 is x squared
and x^3 is x cubed etc.

Cheers mate

one more question mate, bit cheeky of me i know sorry.
Solve the following quadratic equation by implementing the formula method.
Answer to 3 significant figures
Can you Show each step to the solution please.
5x2 + 5x – 4x2 + 2x= 20

The standard form of the quadratic equation is
Ax2 + bx + c = 0

How would this be solved??

5x2 + 5x – 4x2 + 2x= 20
take x terms together n x^2 trems together
so u get

x^2+7x-20=0
u cannot factorise thie equation
if d equation is ax^2+bx+c=0
so use (-b+sq(b^2-4ac))/2a n (-b-sq(b^2-4ac))/2a
these two r the values of x
i guess u know this