Question

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Answer 1

there you go

Answer 2

$$y=2x^2+6x-20$$ substitute y=0,
$$0=2x^2+6x-20$$ find the roots of the eqn. answers are the x-intercepts.
For the second question, factorize the terms that is having the degree of 2 (ie x^2+8x+15 and x^2-16) also note that 2 can be taken out from 2x+6. Then you can see that some terms cut off

Answer 3

All terms are multiples of two, so factor it out
2(x^2 + 3 - 10) = 0
2(x + 5)(x - 2) = 0
x = - 5, x = 2

Answer 4

the second question we already did two of them

Answer 5

do you want to do it both